Rule based list manipulation

Question

I'm trying to restructure the following expression:

start = Table[{1, 2, 3, 4}, 5];
Join[{ToString /@ {first, second, third, fourth}},start]

Into this:

final =Table[{1, 4, 2, 3}, 5];
Join[{ToString /@ {first, fourth,second, third}},final]

Ideally I would like to do this with rules (i.e. exchange columns). It would be even better if I could do it by the column header name. Please assume the variables are not homogeneous throughout the column.

Thanks!

Answer 1

I think a simple way is just to swap columns directly. Why complicate things?

start = Table[{1, 2, 3, 4}, 5];
start = Join[{ToString /@ {first, second, third, fourth}}, start]

Now just do

start[[All, {2, 3, 4}]] = start[[All, {4, 2, 3}]];

Any reason why not do this?

If you really want to use rule, you could use

start = Table[{1, 2, 3, 4}, 5];
start = Join[{ToString /@ {first, second, third, fourth}}, start];
rules = {2 -> 4, 3 -> 4, 4 -> 1};

start[[All, {2, 3, 4}]] = start[[All, {2, 3, 4} /. rules]];