Hello,

I have a matrix

animal            time              A01                 A02
 A                  d0               -5.4                     2.7
 A                  d112            4.6                     5.9
 A                  d224             3.9                    6.3
 B                  d0                7.1                     5.6
 B                  d112            1.5                     3.2
 B                  d224             2.9                    3.6
 C                  d112            3.7                     5.8
 C                  d0                7.1                     NA
 C                 d224            4.2                       5.7

I have three animal A, B, C. Each animal have two measurements(A01 and A02)
at three different time points (d0, d112 and d224).  I'd like to calculate:

animal A:

A01 at d112 (4.6) - A01 at d0 (-5.4)
A01 at d224 (3.9) - A01 at d0 (-5.4)

A02 at d112 (5.9) - A02 at d0 (2.7)
A02 at d224 (6.3) - A02 at d0 (2.7)

Same for animal B and C

I really appreciate your help.

Junyu

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