Dear R group,

I have a query about summarizing the sub groups. I want to calculate mean
or median of  BMI & SWTZ of ID 1 to 3 as shown in below table. Actually I
have 4500 ID's.
I appreciate your assistance and guidance.

  ID BMI SWTZ  1 22.3 97.7  1 22.3 116  1 22.3 116  1 22.3 110.8  1 22.3
110.8  2 27.3 135.8  2 23 119  2 29.4 65.4  2 29.4 65.4  2 29.4 65.4  3 22.3
128.1  3 22.3 128.1  3 22.3 128.1  3 22.3 128.1  3 22.3 114.7

Thank you very much in advance.
-- 
Regards,

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