floating point / no data source code

[Olga Waupotitsch]

s.cox at dem.csiro.au (Simon Cox) writes:


>>>All the GRASS commands you are used to will still work
>>>as they did before except that newly
>>>modified programs will treat 0's in your old maps as no data cells.
 
>What about us poor people who have old maps where 0=zero?  What do you
>suggest we do??  I am quite concerned that I am going to left with a large
>number of maps that do not behave how I need them to any more.  I suggest
>that with the introduction of such a radical change that it is fairly
>irresponsible to leave some of us in the lurch.  At least provide a utility
>to allow me to convert my old maps into the new format.  I don't think that
>this is my job either since it is the software that has been changed, not
>my data.
 
>Simon Cox

I modified r.support to have an option to crerate a null file for your
existing map describing all cells as valid data (i.e. after running it for
your map, 0's will be 0's , not nulls.

Here is the new interface:
Enter name of raster file for which you will create/modify support files
Enter 'list' for a list of existing raster files
Enter 'list -f' for a list with titles
Hit RETURN to cancel request
> asp.i
<asp.i>
Edit the header for [asp.i]? (y/n) [n]
Update the stats (histogram,range) for [asp.i]? (y/n) [n]
Edit the category file for [asp.i]? (y/n) [n]
Create/Update the color table for [asp.i]? (y/n) [n]
Edit the history file for [asp.i]? (y/n) [n]

The null file for [asp.i] might indicate that some cells contain
no data. If null file for [asp.i] doesn't exist all zero cells in [asp.i]
are treated by GRASS application programs as no data.

Do you want to create/reset null file for [asp.i] so that
all cell values are considered valid data? (y/n) [n]

Do you want to delete null file for [asp.i]
(all zero cells will then be considered no data)? (y/n) [n]

Also we are planning to write a new program: r.null
so that one can specify which values in the map are nulls, and
which are valid. Please see my home page for more info
on this.
Olga