how to use MatrixForm on a matrix after applying NumberForm on it?

Question

V 12.1 on windows.

I do not remember if I've seen this and googling is not helping.

I wanted to format a numerical matrix for display using MatrixForm. But first I wanted to apply NumberForm on each entry, because I wanted all entries to have same width when displayed (so they do not shift around during display and running.

But NumberForm does not work well with MatrixForm. Is there a way around this?

a = {{1.3432, 34.432123}, {5.65454, 78.9883}}
MatrixForm[a]

And now

a = {{1.3432, 34.432123}, {5.65454, 78.9883}};
b = NumberForm[a, {2, 2}]

And it is the above I want to display in MatrixForm But it does not work on it due to the NumberForm wrapper in between

 MatrixForm[b]

Also doing things in reverse ofcourse does not work either

 NumberForm@MatrixForm[a]

I could ofcourse use Round on the matrix first, then apply MatrixForm but I prefer to use things like NumberForm and AccountingForm since they allow more control on the format.

Is there a better way to do the above?

Answer 1

Export suffers similar problem. The solution I found is, use *Form only on numbers:

a = {{1.3432, 34.432123}, {5.65454, 78.9883}};
Clear[numberForm]
numberForm[a_List, n_] := numberForm[#, n] & /@ a
numberForm[a_, n_] := NumberForm[a, n]
b = numberForm[a, {2, 2}]
MatrixForm@b