[GIS] Log or Ln function in QGIS Field Calculator

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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 that works.

I'm using 1.4.0 on linux currently. I couldn't find anything in release notes about this being added since, but does anyone know if it's in a newer release?

Many thanks!

Best Answer

Asked functions added to QGIS

http://hub.qgis.org/issues/4365#note-1

This is how it (the QGIS project) works... just ask, if it make sense it will be probably be added in a short time ;)

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[GIS] QGIS field-calculator replace function

It's giving you that error because it's the wrong syntax. The OR and AND keywords return true or false. The replace function is for strings so you don't really need it here. What you are looking for is the case expression:

CASE WHEN NAME="4600" OR NAME="4700" OR NAME="4800" THEN 1 END

Note: You need to be running the dev build of QGIS to get that function

[GIS] Using replace string function in QGIS Field Calculator

replace( '(B)','(B)','County')

tells QGIS to replace the '(B)' in '(B)' with 'Country'.

You want

replace("Name",'(B)','Country')

= replace the '(B)' in "Name" with 'Country'.

Note that the double quotes indicate a field name while the single quotes refer to a static string. These are not interchangeable.

Best Answer

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