Tagged Questions

1
vote
1answer
27 views

QGIS Field Calculation convert to ArcGIS

I have a field calculator expression I use in QGIS to generate unique IDs that are sequential, but start with a text string. I now need to perform the same thing in ArcGIS, but I am unsure of how to ...
0
votes
1answer
69 views

How to calculate polygon areas in acres or square miles instead of feet?

I have a layer in State Plane NAD83. When I use "Vector|Geometry Tools|Add/export geometry columns" or Field Calculator they both create the area in feet. What if I want acres or square miles? Thanks ...
2
votes
2answers
77 views

Capitalizing The First Letter Of Each Word In Attribute Field

Does anyone know of a way to capitalize the first letter of each word in a field in an attribute table? I am doing this in QGIS. I know of field calculations to change all the words to Lower or ...
0
votes
0answers
20 views

Exporting QGIS attribute table to excel [duplicate]

I have a million rows in the attribute table, with lat/lon columns that I want to export to Excel. Selecting all the rows causes QGIS to crash. Is there another way to do the export? The million rows ...
1
vote
2answers
77 views

area values determined with field calculator become null when saving

using field calculator in Qgis 1.8.0 to get the area, it shows just right at first but when I save it, the values become Null. help please
3
votes
2answers
67 views

QGIS Field Calculator Results Removed When Saving Edits

Mac OSX 10.6.8 QGIS 1.8.0 : Using the field calculator from the attribute table, the $area of each feature is shown nicely in the table until I try to save it, then all the values are replaced by NULL ...
1
vote
1answer
76 views

How to create a label formatted like “ 1,000' ” from a numeric field?

This question builds on a previous question I came across at gis.stackexchange: How to easily edit attribute data using Regular Expressions? Perhaps someone can point me in the right direction? I ...
0
votes
0answers
26 views

How to populate polygon extents to an attribute table in QGIS

Is there a way to calculate the XMIN, YMIN, XMAX and YMAX of a polygon and write it to a field in an attribute table? The Geometry functions available in the Field Calculator are for points. ...
3
votes
2answers
127 views

Field Calculator decimal places - how can I limit them?

I've added a new column to an attribute table and performed an operation with the field calculator to populate the new column. The result is a column with a percentage. My problem isn't major but I ...
5
votes
1answer
105 views

How to add attributes in proportion to intersecting area from another layer

I am new to using QGIS. I have two polygon layers: Voronoi of Access Points Census block maps with population I want to get number of people covered by each Access Point (Assuming uniform ...
5
votes
2answers
93 views

Using field calculator to delete specific contours

I have 3 contour shapefiles with 25m, 50m and 100m equidistance. Now I want to delete in the 25m-shp-file every **50m and **00m contour and in the 50m-shp-file every **00 contour. How can I show them ...
3
votes
3answers
183 views

Auto-calculate field (area or formula)

I'm wondering if anyone has any insight into the potential to auto-calculate the value of a field, either area or distance (ideally) or a formula (based on the values of say 2 other fields, or an ...
1
vote
1answer
265 views

How to use field calculator for area calculations in QGis? [duplicate]

Possible Duplicate: Calculate area between contour lines on a DEM with Qgis 1.8.0-Lisboa Based on a DEM of a whole country I have reclassified altitudinal bands with steps of 100 metres ...
2
votes
1answer
386 views

QGIS field-calculator replace function

I've got a Shapefile containing contourlines which I would like to style differently according to their value. For that reason I created a field named "100s" where I would like to give values from ...
0
votes
1answer
103 views

FieldPyculator Plugin - How to concatenate fields?

How can i concatenate two fields using pyculator plugin? There is any document with all pyculator functions that i can use in "field expression"?
1
vote
1answer
552 views

How to do a simple find and replace in QGIS field calculator?

I'm trying to replace selected string values in an attribute table, eg. "Text1" for "Text2" (QGIS 1.8.0), patriculary for those rows with NULL values. I have been trying to use the replace expression ...
2
votes
1answer
140 views

Unit of $length in QGis Field Calculator

I'm calculating field of various features in my shapefile using QGis. I'm getting some sample length as 0.134914579766986. I want to know in what unit (eg: meters, km etc) is the above value ?
5
votes
2answers
202 views

How to add a sequence to the attribute table?

Is there a way to use the field calculator in QGIS to create a range of values in a count sequence with a specified input range? For example, if I wanted to have the values 1 to 5 repeated within my ...
2
votes
1answer
646 views

Elseif Conditional Statement in QGIS Field Calculator

I am trying to write an ELSEIF conditional statement in QGIS Field Calculator (version 1.8.0). I have used an example I found online: CASE WHEN val < 0 THEN 'negative' WHEN val = 0 THEN ...
3
votes
1answer
539 views

How to use field calculator from QGIS Sextante plugin

I am trying to use the Sextante field calculator to calculate a field for a buffer radius using a categorical text field. The formula works fine when I run it using the standard QGIS field calculator ...
5
votes
1answer
443 views

How to measure area correctly?

I have now used my entire evening, but I can't figure out how to make areal calculations (eg. in km2). I have tried the 'field calculator', I have tried the 'measure area' function on the "attributes" ...
3
votes
1answer
120 views

Measurement units not returned in project CRS units

I am attempting to calculate area of country polygons using the field calculator. The layer in question is unprojected WGS84, but I have set the project CRS to World Equidistant Cylindrical ...
2
votes
2answers
353 views

Trimming Specific Text Values in QGIS Field Calculator

Sorry if this is a dumb question, but I am wondering if there is a way to copy the text from one field to a new field, but eliminate specific words. For example: **Old Field** ...
2
votes
2answers
432 views

FIeld calculator gives integer not a real as requested

Two fields "population" and "F06_popula" (both integers) were used in calculating a new field pct-diff. I asked that the new field be a decimal with a width of 10 and precision of 3. The result has ...
1
vote
3answers
207 views

Automatically assign numbers to point file in various order in QGIS

I know how to automatically assign numbers to a new point files using the $rownum function in the field calculator. However it does it from the top-left over and down like reading a book. I could ...
1
vote
1answer
443 views

Concatenate Fields into One Field in QGIS

I have seen some posts on this, but only for ArcMap. I am looking to take a range of values from two fields and concatenate them into one field to make a unique value. For example: XMAX YMAX ...
5
votes
1answer
371 views

How to fill my column with consecutive numbers

I m very new to Qgis, so forgive this simple question. Searching in older topics didn t help either.So: I make a new column in my attribute table and it has a default value(for example 0). I want to ...
4
votes
1answer
250 views

How to add attribute data up?

Sorry if this question is too simple/easy for you guys, but I'm still learning QGIS and pretty much teaching myself where I can. Is there a way to add data from 2 columns into one new column inside ...
1
vote
2answers
238 views

FieldPyculator Plugin - How to Classify Fields?

Could someone tell me how to classify/populate fields with QGIS FieldPyculator Plugin? In the Attribute Table, I have a field named POPULACAO with population data: I want to apply a weight to ...
5
votes
2answers
336 views

Random value calculation in QGIS

Is there a way to do a random value calculation within a range in QGIS? I have been able to do this within ArcMap Field Calculator with the following code: Dim max, min max=20 min=5 ...
1
vote
1answer
862 views

Do QGIS Field Calculator xat(n) and yat(n) functions work in version 1.7.x?

I'm trying to use the xat(n) and yat(n) in the Field Calculator but can't get them to work. Does anybody have an example how to use them? I need the start and end coordinates for line segments, does ...
2
votes
1answer
426 views

Does QGIS support parsing of date strings in tables?

It is straightforward to load GPX files (GPS downloaded tracks / points) into QGIS, then save and manipulate them as shapefiles. However, the recording date (in the comment (cmt) field) of waypoints ...
4
votes
5answers
737 views

Is there a Log or Ln function in QGIS Field Calculator?

I can't seem to find any way to take the logarithm (natural or base 10) of a field in QGIS. I have gotten to the field calculator but there is not a button for log and I can't seem find any formula ...
7
votes
2answers
2k views

How to calculate perimeter of polygons in Quantum GIS?

Is there a way to calculate perimeter of polygons with the field calculator of qgis, like there is for area calculation?
5
votes
3answers
995 views

Is there a way to concatenate fields in field calculator of QGIS?

Is there a way to concatenate fields in field calculator of QGIS? (e.g. hectares + ' ha')
5
votes
2answers
2k views

Using Field Calculator in QGIS to update columns with centroid coordinates

In QGIS I would like to update two columns with the centroid easting and northing of my polygons. I am using the field calculator. I have tried using $x and $y but this only seems to work for points. ...