Stata interpreting the same string value as different values

[Maria Connor]

I have postcodes in my dataset that I want to group together. As you can see when I type tab Postcode for the majority of values it correctly groups them together. However, for some random postcodes, it counts as different values e.g. CR0 and DA7. I have checked my excel data and it is the same value typed in the cells so I don't understand why Stata identifies it as different values. Does anyone know what the issue might be?

tab Postcode

   Postcode |      Freq.     Percent        Cum.
------------+-----------------------------------
        BR1 |          3        0.50        0.50
        BR2 |          3        0.50        1.00
        CR0 |          7        1.17        3.34
       CR0  |          2        0.33        3.68
        CR2 |          3        0.50        4.18
        CR4 |          4        0.67        4.85
       DA17 |          5        0.84        6.86
        DA7 |          2        0.33        7.19
       DA7  |          1        0.17        7.36

[Leonardo Guizzetti]

Very likely that you have trailing spaces for two of your postal codes. Try the following, then see what you get.

replace Postcode = ustrtrim(Postcode)
tab Postcode

[Maria Connor]

Thank you so much for your help! This worked.