Using All in MapAt in Mathematica

Question

I often have a list of pairs, as

data = {{0,0.0},{1,12.4},{2,14.6},{3,25.1}}

and I want to do something, for instance Rescale, to al

Answer 1

Use Part:

data = {{0, 0.0}, {1, 12.4}, {2, 14.6}, {3, 25.1}}

data[[All, 2]] = Rescale @ data[[All, 2]];

data

Create a copy first if you need to. (data2 = data then data2[[All, 2]] etc.)

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Amending my answer to keep up with ruebenko's, this can be made into a function also:

partReplace[dat_, func_, spec__] :=
  Module[{a = dat},
    a[[spec]] = func @ a[[spec]];
    a
  ]

partReplace[data, Rescale, All, 2]

This is quite general is design.