Calculating means

[Amanda Ode]

Dear Stata experts,

I need help creating variables with the mean values of the 'X_A3', 'Y_A3', and 'S_A3' per SampleID and Run. Each sample (SampleID) has 1, 2, or 3 Runs. This is an example of the data:

* Example generated by -dataex-. To install: ssc install dataex
clear
input long SampleID byte Run double(X_A3 Y_A3) int S_A3
45635001 1             4.95 5.20999999999999 142
45635001 2 4.96999999999999             5.11 142
45635002 1             4.49                5 148
45635002 2             4.44             4.99 147
45635003 1             9.31 5.12999999999999 172
45635004 1             9.58             5.15 169
45635004 2 7.13999999999999             4.45 135
45635004 3             7.07              4.4 135
45635005 1 4.21999999999999             4.79 147
45635005 2             4.19             4.82 147
45635006 1 6.45999999999999 4.58999999999999 137
45635006 2             6.53 4.54999999999999 138
45635007 1              4.5             4.79 144
45635007 2 4.50999999999999 4.75999999999999 145
45635008 1 5.54999999999999             4.23 135
45635009 1 5.16999999999999              4.9 152
45635009 2 5.17999999999999 4.87999999999999 153
45635009 3              5.2             4.57 155
45635010 1             5.28             4.54 133
45635011 1             6.16             4.82 135
45635011 2 6.05999999999999             4.74 133
45635012 1             4.74             4.83 149
45635012 2 4.79999999999999 4.76999999999999 151
45635013 1 4.71999999999999             4.95 143
45635013 2              4.7             4.95 143
45635014 1             3.47 4.42999999999999 153
45635014 2 3.47999999999999              4.4 152
45635015 1 5.26999999999999 5.33999999999999 153
45635015 2             5.29             5.28 153
45635016 1             8.38 4.20999999999999 104
45635016 2 8.36999999999999 4.20999999999999 104
45635017 1 7.91999999999999 3.79999999999999  91
45635017 2             7.57 3.75999999999999  91
45635018 1 7.12999999999999 5.67999999999999 172
45635018 2              7.2             5.65 172
end

The new variables could preferably have the same variable names, i.e., 'X_A3', 'Y_A3', and 'S_A3'. I appreciate your help with the appropriate command(s).

Thank you in advance.
Best,
Amanda

[Amanda Ode]

Hello again,

I just want to clarify my question as I realize it is not clear enough. Each blood sample (variable SampleID) is analyzed once, twice or three times. The number of times each sample is analyzed is found in the variable Run. The results from each analysis is presented in 'X_A3', 'Y_A3', and 'S_A3' parameters. I want to calculate the mean of the run results for each sample, and the new 'X_A3', 'Y_A3', and 'S_A3' shall have only one value (the mean) per sample.

Thank you.