How to calculate the conditional proabability?

I have a data set (attached) and I need to calculate the probability of non zero in row 2 given the event of a non zero in row 1 (I'm ignoring the dates). I'm struggling with the code for this. Can anyone help me?

Answer 1

[Jeff Miller]

Crude, but maybe illustrative:

all=readtable('RainTampa.txt','headerlines',31)
nonzeroVar2 = all(all.Var2~=0,:);
nonzeroVar2and3 = nonzeroVar2(nonzeroVar2.Var3~=0,:);
CondProb = height(nonzeroVar2and3) / height(nonzeroVar2)