Variable counting the number of times another variable takes on a certain value.

[Jad Tamimi]

Hello,

I have data which looks similar to this:

* Example generated by -dataex-. For more info, type help dataex
clear
input float(isic3_3d class)
151 1
151 2
151 2
151 1
151 2
151 2
151 1
151 2
151 2
151 1
151 2
151 2
151 1
151 1
151 2
151 2
151 1
151 1
151 2
151 2
151 2
151 1
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 1
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 1
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
151 2
end
label values class x
label def x 1 "Intermediate", modify
label def x 2 "Consumption", modify

In this sample of my data there is only one value for isic3_3d, but in my data I have many values for this variable, here it only ever equals 151. I would like to create a variable which indicates the number of times the isic3_3d observation takes on the value 1 for class, when doing a simple count it would look like this:

count if isic3_3d==151 & class==1

Whilst it's not illustrated here, I have many values of isic3_3d so I would like to create a variable which calculates the number of times class==1 by the variable isic3_3d. So for example, for all entries with isic3_3d ==151 this variable would take on the same value and it would take the value of "count if isic3_3d==151 & class==1". Then for all entries where isic3_3d equals say 152, this variable would take on the value of "count if isic3_3d==152 & class==1".

Please let me know how I can implement this.

Thanks,
Jad

[George Ford]

egen countvar= count(cond(class==1,isic3_3d,.)), by(isic3_3d)

[Nick Cox]

egen wanted = total(class == 1), by(isic3_2d)

See also https://journals.sagepub.com/doi/pdf...867X1101100210 for some other tricks in this territory.