[GRASS-SVN] r32989 - grass/trunk/raster/r.mapcalc
svn_grass at osgeo.org
svn_grass at osgeo.org
Thu Aug 21 22:01:53 EDT 2008
Author: glynn
Date: 2008-08-21 22:01:53 -0400 (Thu, 21 Aug 2008)
New Revision: 32989
Modified:
grass/trunk/raster/r.mapcalc/Makefile
grass/trunk/raster/r.mapcalc/r.mapcalc.html
grass/trunk/raster/r.mapcalc/r3.mapcalc.html
Log:
{r,r3}.mapcalc now use G_parser(), so use htmlmulti
Use spaces instead of tabs in <pre> sections (works better with manpages)
Synchronise r3.mapcalc to r.mapcalc
Modified: grass/trunk/raster/r.mapcalc/Makefile
===================================================================
--- grass/trunk/raster/r.mapcalc/Makefile 2008-08-22 01:56:48 UTC (rev 32988)
+++ grass/trunk/raster/r.mapcalc/Makefile 2008-08-22 02:01:53 UTC (rev 32989)
@@ -2,6 +2,7 @@
PGM2 = r.mapcalc
PGM3 = r3.mapcalc
+PROGRAMS = $(PGM2) $(PGM3)
EXTRA_HEADERS = y.tab.h
EXTRA_CLEAN_FILES = y.tab.c y.tab.h lex.yy.c y.output lex.backup
@@ -84,7 +85,7 @@
LIBES2 = $(GISLIB) $(BTREELIB) $(ROWIOLIB) $(READLINELIBPATH) $(READLINELIB) $(HISTORYLIB)
LIBES3 = $(G3DLIB) $(GISLIB) $(BTREELIB) $(READLINELIBPATH) $(READLINELIB) $(HISTORYLIB)
-default: $(BIN)/$(PGM2)$(EXE) $(BIN)/$(PGM3)$(EXE) html
+default: $(BIN)/$(PGM2)$(EXE) $(BIN)/$(PGM3)$(EXE) htmlmulti
$(BIN)/$(PGM2)$(EXE): $(LIST2) $(DEPLIBS2)
$(CC) $(LDFLAGS) -o $@ $(LIST2) $(FMODE_OBJ) $(LIBES2) $(MATHLIB) $(XDRLIB)
@@ -97,8 +98,3 @@
lex.yy.c: mapcalc.l y.tab.h
$(LEX) -t mapcalc.l > $@
-
-html:
- $(MKDIR) $(GISBASE)/docs/html
- $(INSTALL_DATA) $(PGM2).html $(GISBASE)/docs/html/
- $(INSTALL_DATA) $(PGM3).html $(GISBASE)/docs/html/
Modified: grass/trunk/raster/r.mapcalc/r.mapcalc.html
===================================================================
--- grass/trunk/raster/r.mapcalc/r.mapcalc.html 2008-08-22 01:56:48 UTC (rev 32988)
+++ grass/trunk/raster/r.mapcalc/r.mapcalc.html 2008-08-22 02:01:53 UTC (rev 32989)
@@ -1,14 +1,3 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
-<html>
-<head>
-<title>r.mapcalc</title>
-<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
-<link rel="stylesheet" href="grassdocs.css" type="text/css">
-</head>
-<body bgcolor="white">
-<img src="grass_logo.png" alt="GRASS logo"><hr align=center size=6 noshade>
-<h2>NAME</h2>
-<em><b>r.mapcalc</b></em>
<h2>DESCRIPTION</h2>
<em>r.mapcalc</em> performs arithmetic on raster map layers.
New raster map layers can be created which are arithmetic expressions
@@ -174,16 +163,16 @@
(representing soil pH values) has a category file with labels as follows:
<p>
<div class="code"><pre>
-cat label
+cat label
------------------
-0 no data
-1 1.4
-2 2.4
-3 3.5
-4 5.8
-5 7.2
-6 8.8
-7 9.4
+0 no data
+1 1.4
+2 2.4
+3 3.5
+4 5.8
+5 7.2
+6 8.8
+7 9.4
</pre></div>
<p>
Then the expression:
@@ -292,41 +281,41 @@
are floating point values and integer if all arguments are integer.
<p>
<div class="code"><pre>
-function description type
+function description type
---------------------------------------------------------------------------
-abs(x) return absolute value of x *
-acos(x) inverse cosine of x (result is in degrees) F
-asin(x) inverse sine of x (result is in degrees) F
-atan(x) inverse tangent of x (result is in degrees) F
-atan(x,y) inverse tangent of y/x (result is in degrees) F
-cos(x) cosine of x (x is in degrees) F
-double(x) convert x to double-precision floating point F
-eval([x,y,...,]z) evaluate values of listed expr, pass results to z
-exp(x) exponential function of x F
-exp(x,y) x to the power y F
-float(x) convert x to single-precision floating point F
-graph(x,x1,y1[x2,y2..]) convert the x to a y based on points in a graph F
-if decision options: *
-if(x) 1 if x not zero, 0 otherwise
-if(x,a) a if x not zero, 0 otherwise
-if(x,a,b) a if x not zero, b otherwise
-if(x,a,b,c) a if x > 0, b if x is zero, c if x < 0
-int(x) convert x to integer [ truncates ] I
+abs(x) return absolute value of x *
+acos(x) inverse cosine of x (result is in degrees) F
+asin(x) inverse sine of x (result is in degrees) F
+atan(x) inverse tangent of x (result is in degrees) F
+atan(x,y) inverse tangent of y/x (result is in degrees) F
+cos(x) cosine of x (x is in degrees) F
+double(x) convert x to double-precision floating point F
+eval([x,y,...,]z) evaluate values of listed expr, pass results to z
+exp(x) exponential function of x F
+exp(x,y) x to the power y F
+float(x) convert x to single-precision floating point F
+graph(x,x1,y1[x2,y2..]) convert the x to a y based on points in a graph F
+if decision options: *
+if(x) 1 if x not zero, 0 otherwise
+if(x,a) a if x not zero, 0 otherwise
+if(x,a,b) a if x not zero, b otherwise
+if(x,a,b,c) a if x > 0, b if x is zero, c if x < 0
+int(x) convert x to integer [ truncates ] I
isnull(x) check if x = NULL
-log(x) natural log of x F
-log(x,b) log of x base b F
-max(x,y[,z...]) largest value of those listed *
-median(x,y[,z...]) median value of those listed *
-min(x,y[,z...]) smallest value of those listed *
+log(x) natural log of x F
+log(x,b) log of x base b F
+max(x,y[,z...]) largest value of those listed *
+median(x,y[,z...]) median value of those listed *
+min(x,y[,z...]) smallest value of those listed *
mode(x,y[,z...]) mode value of those listed *
-not(x) 1 if x is zero, 0 otherwise
-pow(x,y) x to the power y *
-rand(a,b) random value x : a <= x < b
-round(x) round x to nearest integer I
-sin(x) sine of x (x is in degrees) F
-sqrt(x) square root of x F
-tan(x) tangent of x (x is in degrees) F
-xor(x,y) exclusive-or (XOR) of x and y I
+not(x) 1 if x is zero, 0 otherwise
+pow(x,y) x to the power y *
+rand(a,b) random value x : a <= x < b
+round(x) round x to nearest integer I
+sin(x) sine of x (x is in degrees) F
+sqrt(x) square root of x F
+tan(x) tangent of x (x is in degrees) F
+xor(x,y) exclusive-or (XOR) of x and y I
</pre></div>
<div class="code"><pre>
Internal variables:
@@ -367,19 +356,19 @@
<ul>
<li>Division by zero should result in NULL.
<li>Modulus by zero should result in NULL.
-<li> NULL-values in any arithmetic or logical operation should result
- in NULL. (however, &&& and ||| are treated specially, as described below).
-<li> The &&& and ||| operators observe the following axioms even when x is NULL:
+<li>NULL-values in any arithmetic or logical operation should result
+in NULL. (however, &&& and ||| are treated specially, as described below).
+<li>The &&& and ||| operators observe the following axioms even when x is NULL:
<div class="code"><pre>
x &&& false == false
false &&& x == false
x ||| true == true
true ||| x == true
</pre></div>
-<li> NULL-values in function arguments should result in NULL (however,
- if(), eval() and isnull() are treated specially, as described below).
-<li> The eval() function always returns its last argument
-<li> The situation for if() is:
+<li>NULL-values in function arguments should result in NULL (however,
+if(), eval() and isnull() are treated specially, as described below).
+<li>The eval() function always returns its last argument
+<li>The situation for if() is:
<div class="code"><pre>
if(x)
NULL if x is NULL; 0 if x is zero; 1 otherwise
@@ -391,9 +380,9 @@
NULL if x is NULL; n if x is negative;
z if x is zero; p if x is positive
</pre></div>
-<li> The (new) function isnull(x) returns: 1 if x is NULL;
- 0 otherwise. The (new) function null()
- (which has no arguments) returns an integer NULL.
+<li>The (new) function isnull(x) returns: 1 if x is NULL;
+0 otherwise. The (new) function null()
+(which has no arguments) returns an integer NULL.
<li>Non-NULL, but invalid, arguments to functions should result in NULL.
<div class="code"><pre>
Examples:
Modified: grass/trunk/raster/r.mapcalc/r3.mapcalc.html
===================================================================
--- grass/trunk/raster/r.mapcalc/r3.mapcalc.html 2008-08-22 01:56:48 UTC (rev 32988)
+++ grass/trunk/raster/r.mapcalc/r3.mapcalc.html 2008-08-22 02:01:53 UTC (rev 32989)
@@ -1,46 +1,35 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
-<html>
-<head>
-<title>r3.mapcalc</title>
-<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
-<link rel="stylesheet" href="grassdocs.css" type="text/css">
-</head>
-<body bgcolor="white">
-<img src="grass_logo.png" alt="GRASS logo"><hr align=center size=6 noshade>
-<H2>NAME</H2>
-<EM><B>r3.mapcalc</B></EM>
-<H2>DESCRIPTION</H2>
-<EM>r3.mapcalc</EM> performs arithmetic on 3D grid volume data. New 3D grids
+<h2>DESCRIPTION</h2>
+<em>r3.mapcalc</em> performs arithmetic on 3D grid volume data. New 3D grids
can be created which are arithmetic expressions involving existing 3D grids,
integer or floating point constants, and functions.
-<H2>PROGRAM USE</H2>
-If used without command line arguments, <EM>r3.mapcalc</EM> will read its
+<h2>PROGRAM USE</h2>
+If used without command line arguments, <em>r3.mapcalc</em> will read its
input, one line at a time, from standard input (which is the keyboard,
unless redirected from a file or across a pipe).
-Otherwise, the expression on the command line is evaluated. <EM>r3.mapcalc</EM>
+Otherwise, the expression on the command line is evaluated. <em>r3.mapcalc</em>
expects its input to have the form:
-<P>
-<B>result=</B><EM>expression</EM>
-<P>
-where <EM>result</EM> is the name of a 3D grid to contain the result of
-the calculation and <EM>expression</EM> is any legal arithmetic expression
+<p>
+<b>result=</b><em>expression</em>
+<p>
+where <em>result</em> is the name of a 3D grid to contain the result of
+the calculation and <em>expression</em> is any legal arithmetic expression
involving existing 3D grid, floating point constants, and functions known
to the calculator. Parentheses are allowed in the expression and may be
-nested to any depth. <EM>result</EM> will be created in the user's current
+nested to any depth. <em>result</em> will be created in the user's current
mapset.
-<P>
-The formula entered to <EM>r3.mapcalc</EM> by the user is recorded both
-in the <EM>result</EM> grid title (which appears in the category file for
-<EM>result</EM>)
-and in the history file for <EM>result</EM>.
-<P>
+<p>
+The formula entered to <em>r3.mapcalc</em> by the user is recorded both
+in the <em>result</em> grid title (which appears in the category file for
+<em>result</em>)
+and in the history file for <em>result</em>.
+<p>
Some characters have special meaning to the command shell. If the user
-is entering input to <EM>r.mapcalc</EM> on the command line, expressions
+is entering input to <em>r.mapcalc</em> on the command line, expressions
should be enclosed within single quotes. See NOTES, below.
-<P>
-<H2>OPERATORS AND ORDER OF PRECEDENCE</H2>
+<p>
+<h2>OPERATORS AND ORDER OF PRECEDENCE</h2>
The following operators are supported:
-<div class="code"><PRE>
+<div class="code"><pre>
Operator Meaning Type Precedence
--------------------------------------------------------------
- negation Arithmetic 12
@@ -68,148 +57,148 @@
|| logical or Logical 2
||| logical or[1] Logical 2
?: conditional Logical 1
-</PRE></div>
+</pre></div>
(modulus is the remainder upon division)
-<P>
+<p>
[1] The &&& and ||| operators handle null values differently to other
operators. See the section entitled <b>NULL support</b> below for more
details.
-<P>
+<p>
The operators are applied from left to right, with those of higher precedence
applied before those with lower precedence.
Division by 0 and modulus by 0 are acceptable and give a NULL result.
The logical operators give a 1 result if the comparison is true, 0 otherwise.
-<P>
-<P>
-<H2>3D GRID NAMES</H2>
+<p>
+<p>
+<h2>3D GRID NAMES</h2>
Anything in the expression which is not a number, operator, or function
name is taken to be a 3D grid name. Examples:
-<P>
-<div class="code"><PRE>
+<p>
+<div class="code"><pre>
volume
x3
3d.his
-</PRE></div>
-<P>
+</pre></div>
+<p>
Most GRASS raster map layers and 3D grids meet this naming convention.
However, if a 3D grid has a name which conflicts with the above rule, it
should be quoted. For example, the expression
-<P>
-<div class="code"><PRE>
+<p>
+<div class="code"><pre>
x = a-b
-</PRE></div>
-<P>
+</pre></div>
+<p>
would be interpreted as: x equals a minus b, whereas
-<P>
-<div class="code"><PRE>
+<p>
+<div class="code"><pre>
x = "a-b"
-</PRE></div>
-<P>
-would be interpreted as: x equals the 3D grid named <EM>a-b</EM>
-<P>
+</pre></div>
+<p>
+would be interpreted as: x equals the 3D grid named <em>a-b</em>
+<p>
Also
-<P>
-<div class="code"><PRE>
+<p>
+<div class="code"><pre>
x = 3107
-</PRE></div>
-<P>
-would create <EM>x</EM> filled with the number 3107, while
-<P>
-<div class="code"><PRE>
+</pre></div>
+<p>
+would create <em>x</em> filled with the number 3107, while
+<p>
+<div class="code"><pre>
x = "3107"
-</PRE></div>
-<P>
-would copy the 3D grid <EM>3107</EM> to the 3D grid <EM>x</EM>.
+</pre></div>
+<p>
+would copy the 3D grid <em>3107</em> to the 3D grid <em>x</em>.
-<P>
+<p>
Quotes are not required unless the 3D grid names look like numbers or
contain operators, OR unless the program is run non-interactively. Examples
given here assume the program is run interactively. See NOTES, below.
-<P>
-<EM>r3.mapcalc</EM> will look for the 3D grids according to the user's
+<p>
+<em>r3.mapcalc</em> will look for the 3D grids according to the user's
current mapset search path. It is possible to override the search path
and specify the mapset from which to select the 3D grid. This is done by
specifying the 3D grid name in the form:
-<P>
-<div class="code"><PRE>
+<p>
+<div class="code"><pre>
name at mapset
-</PRE></div>
-<P>
+</pre></div>
+<p>
For example, the following is a legal expression:
-<P>
-<div class="code"><PRE>
+<p>
+<div class="code"><pre>
result = x at PERMANENT / y at SOILS
-</PRE></div>
-<P>
+</pre></div>
+<p>
The mapset specified does not have to be in the mapset search path. (This
method of overriding the mapset search path is common to all GRASS commands,
-not just <EM>r3.mapcalc</EM>.)
-<P>
-<H2>THE NEIGHBORHOOD MODIFIER</H2>
+not just <em>r3.mapcalc</em>.)
+<p>
+<h2>THE NEIGHBORHOOD MODIFIER</h2>
3D grids are data base files stored in voxel format, i.e., three-dimensional
-matrices of float/double values. In <EM>r3.mapcalc</EM>, 3D grids may be
-followed by a <EM>neighborhood</EM> modifier that specifies a relative offset
+matrices of float/double values. In <em>r3.mapcalc</em>, 3D grids may be
+followed by a <em>neighborhood</em> modifier that specifies a relative offset
from the current cell being evaluated. The format is
-<EM>map[r,c,d]</EM>,
-where <EM>r</EM> is the row offset, <EM>c</EM> is the column offset and <EM>d</EM>
-is the depth offset. For example, <EM>map[1,2,3]</EM> refers to the cell
+<em>map[r,c,d]</em>,
+where <em>r</em> is the row offset, <em>c</em> is the column offset and <em>d</em>
+is the depth offset. For example, <em>map[1,2,3]</em> refers to the cell
one row below, two columns to the right and 3 levels below of the current
-cell, <EM>map[-3,-2,-1]</EM> refers to the cell three rows above, two columns
-to the left and one level below of the current cell, and <EM>map[0,1,0]</EM>
+cell, <em>map[-3,-2,-1]</em> refers to the cell three rows above, two columns
+to the left and one level below of the current cell, and <em>map[0,1,0]</em>
refers to the cell one column to the right of the current cell. This syntax
permits the development of neighborhood-type filters within a single 3D
grid or across multiple 3D grids.
-<P>
-<H2>FUNCTIONS</H2>
+<p>
+<h2>FUNCTIONS</h2>
The functions currently supported are listed in the table below.
The type of the result is indicated in the last column.
-<EM>F</EM>
+<em>F</em>
means that the functions always results in a floating point value,
-<EM>I</EM>
+<em>I</em>
means that the function gives an integer result, and
-<EM>*</EM>
+<em>*</em>
indicates that the result is float if any of the arguments to the function
are floating point values and integer if all arguments are integer.
-<P>
-<div class="code"><PRE>
-function description type
+<p>
+<div class="code"><pre>
+function description type
---------------------------------------------------------------------------
-abs(x) return absolute value of x *
-acos(x) inverse cosine of x (result is in degrees) F
-asin(x) inverse sine of x (result is in degrees) F
-atan(x) inverse tangent of x (result is in degrees) F
-atan(x,y) inverse tangent of y/x (result is in degrees) F
-cos(x) cosine of x (x is in degrees) F
-double(x) convert x to double-precision floating point F
-eval([x,y,...,]z) evaluate values of listed expr, pass results to z
-exp(x) exponential function of x F
-exp(x,y) x to the power y F
-float(x) convert x to single-precision floating point F
-graph(x,x1,y1[x2,y2..]) convert the x to a y based on points in a graph F
-if decision options: *
-if(x) 1 if x not zero, 0 otherwise
-if(x,a) a if x not zero, 0 otherwise
-if(x,a,b) a if x not zero, b otherwise
-if(x,a,b,c) a if x > 0, b if x is zero, c if x < 0
-int(x) convert x to integer [ truncates ] I
+abs(x) return absolute value of x *
+acos(x) inverse cosine of x (result is in degrees) F
+asin(x) inverse sine of x (result is in degrees) F
+atan(x) inverse tangent of x (result is in degrees) F
+atan(x,y) inverse tangent of y/x (result is in degrees) F
+cos(x) cosine of x (x is in degrees) F
+double(x) convert x to double-precision floating point F
+eval([x,y,...,]z) evaluate values of listed expr, pass results to z
+exp(x) exponential function of x F
+exp(x,y) x to the power y F
+float(x) convert x to single-precision floating point F
+graph(x,x1,y1[x2,y2..]) convert the x to a y based on points in a graph F
+if decision options: *
+if(x) 1 if x not zero, 0 otherwise
+if(x,a) a if x not zero, 0 otherwise
+if(x,a,b) a if x not zero, b otherwise
+if(x,a,b,c) a if x > 0, b if x is zero, c if x < 0
+int(x) convert x to integer [ truncates ] I
isnull(x) check if x = NULL
-log(x) natural log of x F
-log(x,b) log of x base b F
-max(x,y[,z...]) largest value of those listed *
-median(x,y[,z...]) median value of those listed *
-min(x,y[,z...]) smallest value of those listed *
+log(x) natural log of x F
+log(x,b) log of x base b F
+max(x,y[,z...]) largest value of those listed *
+median(x,y[,z...]) median value of those listed *
+min(x,y[,z...]) smallest value of those listed *
mode(x,y[,z...]) mode value of those listed *
-not(x) 1 if x is zero, 0 otherwise
-pow(x,y) x to the power y *
-rand(a,b) random value x : a <= x < b
-round(x) round x to nearest integer I
-sin(x) sine of x (x is in degrees) F
-sqrt(x) square root of x F
-tan(x) tangent of x (x is in degrees) F
-xor(x,y) exclusive-or (XOR) of x and y I
-</PRE></div>
-<div class="code"><PRE>
+not(x) 1 if x is zero, 0 otherwise
+pow(x,y) x to the power y *
+rand(a,b) random value x : a <= x < b
+round(x) round x to nearest integer I
+sin(x) sine of x (x is in degrees) F
+sqrt(x) square root of x F
+tan(x) tangent of x (x is in degrees) F
+xor(x,y) exclusive-or (XOR) of x and y I
+</pre></div>
+<div class="code"><pre>
Internal variables:
row() current row of moving window
col() current col of moving window
@@ -221,14 +210,14 @@
nsres() current north-south resolution
tbres() current top-bottom resolution
null() NULL value
-</PRE></div>
+</pre></div>
Note, that the row(), col() and depth() indexing starts with 1.
-<H2>FLOATING POINT VALUES IN THE EXPRESSION</H2>
+<h2>FLOATING POINT VALUES IN THE EXPRESSION</h2>
Floating point numbers are allowed in the expression. A floating point
number is a number which contains a decimal point:
-<div class="code"><PRE>
+<div class="code"><pre>
2.3 12.0 12. .81
-</PRE></div>
+</pre></div>
Floating point values in the expression are handled in a special way.
With arithmetic and logical operators, if either operand is float,
the other is converted to float and the result of the operation is float.
@@ -236,35 +225,35 @@
(truncated) integer, while division of floats results in an accurate
floating point value. With functions of type * (see table above),
the result is float if any argument is float, integer otherwise.
-<P>
+<p>
Note: If you calculate with integer numbers, the resulting map will
be integer. If you want to get a float result, add the decimal point
to integer number(s).
-<P>
+<p>
If you want floating point division, at least one of the arguments has
to be a floating point value. Multiplying one of them by 1.0 will
produce a floating-point result, as will using float():
-<div class="code"><PRE>
+<div class="code"><pre>
r.mapcalc "ndvi=float(lsat.4 - lsat.3) / (lsat.4 + lsat.3)"
-</PRE></div>
-<H2>NULL support</H2>
+</pre></div>
+<h2>NULL support</h2>
<ul>
<li>Division by zero should result in NULL.
<li>Modulus by zero should result in NULL.
-<li> NULL-values in any arithmetic or logical operation should result
- in NULL. (however, &&& and ||| are treated specially, as described below).
-<li> The &&& and ||| operators observe the following axioms even when x is NULL:
-<div class="code"><PRE>
+<li>NULL-values in any arithmetic or logical operation should result
+in NULL. (however, &&& and ||| are treated specially, as described below).
+<li>The &&& and ||| operators observe the following axioms even when x is NULL:
+<div class="code"><pre>
x &&& false == false
false &&& x == false
x ||| true == true
true ||| x == true
-</PRE></div>
-<li> NULL-values in function arguments should result in NULL (however,
- if(), eval() and isnull() are treated specially, as described below).
-<li> The eval() function always returns its last argument
-<li> The situation for if() is:
-<div class="code"><PRE>
+</pre></div>
+<li>NULL-values in function arguments should result in NULL (however,
+if(), eval() and isnull() are treated specially, as described below).
+<li>The eval() function always returns its last argument
+<li>The situation for if() is:
+<div class="code"><pre>
if(x)
NULL if x is NULL; 0 if x is zero; 1 otherwise
if(x,a)
@@ -274,19 +263,19 @@
if(x,n,z,p)
NULL if x is NULL; n if x is negative;
z if x is zero; p if x is positive
-</PRE></div>
-<li> The (new) function isnull(x) returns: 1 if x is NULL;
- 0 otherwise. The (new) function null()
- (which has no arguments) returns an integer NULL.
+</pre></div>
+<li>The (new) function isnull(x) returns: 1 if x is NULL;
+0 otherwise. The (new) function null()
+(which has no arguments) returns an integer NULL.
<li>Non-NULL, but invalid, arguments to functions should result in NULL.
-<div class="code"><PRE>
+<div class="code"><pre>
Examples:
log(-2)
sqrt(-2)
pow(a,b) where a is negative and b is not an integer
-</PRE></div>
+</pre></div>
</ul>
-<P>
+<p>
NULL support: Please note that any math performed with NULL cells always
results in a NULL value for these cells. If you want to replace a NULL cell
on-the-fly, use the isnull() test function in a if-statement.
@@ -294,40 +283,40 @@
Example: The users wants the NULL-valued cells to be treated like zeros. To
add maps A and B (where B contains NULLs) to get a map C the user can use a
construction like:<p>
-<div class="code"><PRE>
+<div class="code"><pre>
C=A + if(isnull(B),0,B)
-</PRE></div>
+</pre></div>
<p>
<b>NULL and conditions:</b>
<p>
For the one argument form:
-<div class="code"><PRE>
+<div class="code"><pre>
if(x) = NULL if x is NULL
if(x) = 0 if x = 0
if(x) = 1 otherwise (i.e. x is neither NULL nor 0).
-</PRE></div>
+</pre></div>
<p>
For the two argument form:
-<div class="code"><PRE>
+<div class="code"><pre>
if(x,a) = NULL if x is NULL
if(x,a) = 0 if x = 0
if(x,a) = a otherwise (i.e. x is neither NULL nor 0).
-</PRE></div>
+</pre></div>
<p>
For the three argument form:
-<div class="code"><PRE>
+<div class="code"><pre>
if(x,a,b) = NULL if x is NULL
if(x,a,b) = b if x = 0
if(x,a,b) = a otherwise (i.e. x is neither NULL nor 0).
-</PRE></div>
+</pre></div>
<p>
For the four argument form:
-<div class="code"><PRE>
+<div class="code"><pre>
if(x,a,b,c) = NULL if x is NULL
if(x,a,b,c) = a if x > 0
if(x,a,b,c) = b if x = 0
if(x,a,b,c) = c if x < 0
-</PRE></div>
+</pre></div>
More generally, all operators and most functions return NULL if *any*
of their arguments are NULL.
<br>
@@ -340,7 +329,7 @@
All forms of if() return NULL if the first argument is NULL. The 2, 3
and 4 argument forms of if() return NULL if the "selected" argument is
NULL, e.g.:
-<div class="code"><PRE>
+<div class="code"><pre>
if(0,a,b) = b regardless of whether a is NULL
if(1,a,b) = a regardless of whether b is NULL
</pre></div>
@@ -356,31 +345,31 @@
unknown quantity. E.g. if x and y are both unknown, then the values of
"x == y" and "x != y" are also unknown; if they both have unknown
values, the user doesn't know whether or not they both have the same value.
-<H2>EXAMPLES</H2>
+<h2>EXAMPLES</h2>
To compute the average of two 3D grids
-<EM>a</EM> and <EM>b</EM>:
-<div class="code"><PRE>
+<em>a</em> and <em>b</em>:
+<div class="code"><pre>
ave = (a + b)/2
</pre></div>
To form a weighted average:
-<div class="code"><PRE>
+<div class="code"><pre>
ave = (5*a + 3*b)/8.0
</pre></div>
To produce a binary representation of 3D grid
-<EM>a</EM> so that category 0 remains 0 and all other categories become 1:
-<div class="code"><PRE>
+<em>a</em> so that category 0 remains 0 and all other categories become 1:
+<div class="code"><pre>
mask = a != 0
</pre></div>
This could also be accomplished by:
-<div class="code"><PRE>
+<div class="code"><pre>
mask = if(a)
</pre></div>
-To mask 3D grid <EM>b</EM> by 3D grid <EM>a</EM>:
-<div class="code"><PRE>
+To mask 3D grid <em>b</em> by 3D grid <em>a</em>:
+<div class="code"><pre>
result = if(a,b)
</pre></div>
To change all values below 5 to NULL:
-<div class="code"><PRE>
+<div class="code"><pre>
newmap = if(map<5, null(), 5)
</pre></div>
The graph function allows users to specify a x-y conversion using
@@ -396,11 +385,11 @@
the associated y value returned. Any x value higher than the last
will similarly have the associated y value returned. Consider the
request:
-<div class="code"><PRE>
+<div class="code"><pre>
newmap = graph(map, 1,10, 2,25, 3,50)
</pre></div>
X (map) values supplied and y (newmap) values returned:
-<div class="code"><PRE>
+<div class="code"><pre>
0, 10
1, 10,
1.5, 16.5
@@ -408,87 +397,87 @@
4, 50
100, 50
</pre></div>
-<H2>NOTES</H2>
+<h2>NOTES</h2>
Extra care must be taken if the expression is given on the command line.
Some characters have special meaning to the UNIX shell.
These include, among others:
-<P>
+<p>
* ( ) > & |
-<P>
+<p>
It is advisable to put single quotes around the expression; e.g.:
-<div class="code"><PRE>
+<div class="code"><pre>
result = 'elevation * 2'
</pre></div>
Without the quotes, the *, which has special meaning to the UNIX shell,
-would be altered and <EM>r3.mapcalc</EM> would see something other than the *.
-<P>
-If the input comes directly from the keyboard and the <EM>result</EM>
+would be altered and <em>r3.mapcalc</em> would see something other than the *.
+<p>
+If the input comes directly from the keyboard and the <em>result</em>
3D grid exists, the user will be asked if it can be overwritten. Otherwise,
-the <EM>result</EM> 3D grid will automatically be overwritten if it exists.
-<P>
-Quoting <EM>result</EM> is not allowed. However, it is never necessary
-to quote <EM>result</EM> since it is always taken to be a 3D grid name.
-<P>
+the <em>result</em> 3D grid will automatically be overwritten if it exists.
+<p>
+Quoting <em>result</em> is not allowed. However, it is never necessary
+to quote <em>result</em> since it is always taken to be a 3D grid name.
+<p>
For formulas that the user enters from standard input (rather than from
the command line), a line continuation feature now exists. If the user
-adds \e to the end of an input line, <EM>r3.mapcalc</EM> assumes that the
+adds \e to the end of an input line, <em>r3.mapcalc</em> assumes that the
formula being entered by the user continues on to the next input line.
There is no limit to the possible number of input lines or to the length
of a formula.
-<P>
-If the <EM>r3.mapcalc</EM> formula entered by the user is very long, the
+<p>
+If the <em>r3.mapcalc</em> formula entered by the user is very long, the
map title will contain only some of it, but most (if not all) of the formula
-will be placed into the history file for the <EM>result</EM> map.
-<P>
-When the user enters input to <EM>r3.mapcalc</EM> non-interactively on
+will be placed into the history file for the <em>result</em> map.
+<p>
+When the user enters input to <em>r3.mapcalc</em> non-interactively on
the command line, the program will not warn the user not to overwrite existing
3D grids. Users should therefore take care to assign program outputs 3D
grid file names that do not yet exist in their current mapsets.
-<P>
+<p>
The environment variable GRASS_RND_SEED is read to initialise the
random number generator.
-<H2>BUGS</H2>
+<h2>BUGS</h2>
Continuation lines must end with a \ and have NO trailing white space
(blanks or tabs). If the user does leave white space at the end of
-continuation lines, the error messages produced by <EM>r.mapcalc</EM> will
+continuation lines, the error messages produced by <em>r.mapcalc</em> will
be meaningless and the equation will not work as the user intended.
This is important for the eval() function.
-<P>
-Error messages produced by <EM>r.mapcalc</EM> are almost useless.
-In future, <EM>r.mapcalc</EM> should make some attempt
+<p>
+Error messages produced by <em>r.mapcalc</em> are almost useless.
+In future, <em>r.mapcalc</em> should make some attempt
to point the user to the offending section of the equation, e.g.:
-<div class="code"><PRE>
+<div class="code"><pre>
x = a * b ++ c
ERROR: somewhere in line 1: ... b ++ c ...
</pre></div>
-<P>
-Currently, there is no comment mechanism in <EM>r3.mapcalc</EM>. Perhaps
+<p>
+Currently, there is no comment mechanism in <em>r3.mapcalc</em>. Perhaps
adding a capability that would cause the entire line to be ignored when
the user inserted a # at the start of a line as if it were not present,
would do the trick.
-<P>
+<p>
The function should require the user to type "end" or "exit" instead
of simply a blank line. This would make separation of multiple scripts
separable by white space.
-<P>
+<p>
r.mapcalc does not print a warning in case of operations on NULL cells.
It is left to the user to utilize the isnull() function.
-<H2>SEE ALSO</H2>
-<B><A HREF="http://grass.itc.it/gdp/raster/mapcalc-algebra.pdf">r.mapcalc: An Algebra for GIS and Image
-Processing</A></B>, by Michael Shapiro and Jim Westervelt, U.S. Army
+<h2>SEE ALSO</h2>
+<b><a href="http://grass.itc.it/gdp/raster/mapcalc-algebra.pdf">r.mapcalc: An Algebra for GIS and Image
+Processing</a></b>, by Michael Shapiro and Jim Westervelt, U.S. Army
Construction Engineering Research Laboratory (March/1991).
-<P>
-<B><A HREF="http://grass.itc.it/gdp/raster/mapcalc.pdf">Performing Map Calculations on GRASS Data:
-r.mapcalc Program Tutorial</A></B>, by Marji Larson, Michael Shapiro and Scott
+<p>
+<b><a href="http://grass.itc.it/gdp/raster/mapcalc.pdf">Performing Map Calculations on GRASS Data:
+r.mapcalc Program Tutorial</a></b>, by Marji Larson, Michael Shapiro and Scott
Tweddale, U.S. Army Construction Engineering Research Laboratory (December
1991)
<p>
-<EM><a href="r.mapcalc.html">r.mapcalc</a></EM>
-<H2>AUTHOR</H2>
+<em><a href="r.mapcalc.html">r.mapcalc</a></em>
+<h2>AUTHOR</h2>
Tomas Paudits & Jaro Hofierka, funded by GeoModel s.r.o., Slovakia
<br><a href="mailto:tpaudits at mailbox.sk">tpaudits at mailbox.sk</a>,
<a href="MAILTO:hofierka at geomodel.sk">hofierka at geomodel.sk</a>
-<P>
-<EM>Last changed: $Date$</EM>
+<p>
+<em>Last changed: $Date$</em>
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