[Qgis-user] Newbie Questions

[Michael Lapson]

>
>>  1. I tried doing this with Join Attributes and selecting the CSV file.
>>> However I found that when QGIS reads in the CSV file, it casts all of
>>> the columns as Text, so I couldn't use the numerical values. I notice
>>> the Join Attributes from CSV feature is new in QGIS 1.5.0. Maybe there
>>> is a bug?
>>>
>>>
>>
>> you can do Joins with dbf tables. New join features are being developed.
>>
>>
>>
> In case you're using Excel 2007, you no longer have support for the
> (important) dbf format. So get a copy of Openoffice.org and use that to
> export your tables to dbf. Then number columns will stay as numbers for the
> import to QGIS.
> If there's any problem with the numbers being exported as text, then
> rewrite the column headers in the Excel (OOo Calc) to explicitly make them
> numbers in dbf format. For example a column header like:
> Value,N,10
> will force the dbf column to be numeric with 10 digits.


I am indeed using Excel 2007 and I am hoping for a workflow that goes
directly from Excel to GIS since I do that very often. I tried the
"Value,N,10" trick you describe above but I get an error that the field name
is longer than 10 characters. I assume the CSV table join feature will be
fixed in the next release of QGIS. Is there a way to report and track a bug
like this?


>
>>
>>> 2. Eventually I will want to put my data into a database. I notice I
>>> can choose between SpatiaLite and PostGIS. Which is easier to use? Is
>>> there a performance difference?
>>>
>>>
>>
>> among the others, Postgis is an extension of PostgreSQL, so is server
>> based, spatialite is file based.
>>
>>
>>
> In addition, Spatialite is easy. PostGIS will perform better on huge
> tables.


Thanks for your comments, I am going to try spatialite for now, but I might
switch if my files get bigger.


>>
>>
>>> 3. In ArcMap, I frequently used the capability to vary the thickness
>>> of line features according to a value in the attribute table. I notice
>>> that this capability is available in QGIS only for points ("drawing by
>>> field") but not for line features. Is there another way to accomplish
>>> variable thickness lines in QGIS? If not, is "drawing by field" for
>>> line features under development?
>>>
>>>
>> new symbology ->  advanced ->  size scale field
>>
>>
>>
> I can't seem to get this to work (1.5 on Ubuntu 10.04).
>

It didn't work for me either (1.5.0 Windows 7 x64)

What you can do is categorize the lines then manually give each a different
> line width. In the Old Symbology, choose "Graduated symbol", select the line
> width column and click Classify. Then change the width of each line. Or,
> Using the "New Symbology" , choose "Classified", then again select the
> column and click Classify. Then double click on each symbol to change its
> width.
>

Yes I have tried this and it is very tedious, but sort of works. Not really
the solution I was hoping for.


> Regards,
> Micha
>
>> cheers
>>
>> -- Giovanni --
>>
>> I really appreciate you guys taking the time to think about my questions
and I look forward to seeing continued development of QGIS.

Shalom and Ciao,

Mike

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