I am using QGIS. I've been calculating weighted means based off a database. The database was created by combining two different sets of Data together. The Attribute Table then shows Null values for two reasons: (1) mismatch while joining the two databases together and (2)missing values within the databases themselves.

I have tried to find a logic in the effects Nulls values have on the weighted means but have failed to come to a solid conclusion. They definitely do not act as a ZERO value.

I came across this post in reference to my search: Null values in Geographically Weighted Regression Analysis

It helped explain a lot of things, however this sentence "A null means something entirely different than zero" is the answer to which I am looking for.

What does a Null value mean in weighted mean centers?

  • I believe it will not counted/used in the calculation. – MaxG Jul 25 '16 at 19:43

Null values are simply 'absent'. Meaning you can't find the average of 2 + 2 + absent value. It won't be counted as 0 even though we might want it to.

There might be more elegant workarounds, but you can bring everything into excel via CSV to do your calculations (in the case you have many NULL values) or you can select only the features with a null value and change them to 0.

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