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I know this question. If there are an equal number of columns on each row, then Number of rows: $Length[[MatrixName]]$ and number of columns: $Length[MatrixName[[1]]]$. However, I have a big dataset whose each row does not have an equal number of columns. How can I find the number of rows of a particular column or the number of columns for a particular row?

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SeedRandom[1234];

(mat = Take[#, RandomInteger[{3, 5}]] & /@ 
    Array[a, {10, 10}]) // Column

enter image description here

nbrCol[mat_, row_Integer?Positive] := Length@mat[[row]]

nbrCol[mat, #] & /@ Range[10]

(* {5, 3, 3, 4, 5, 5, 4, 4, 5, 5} *)

nbrRows[mat_, col_Integer?Positive] := 
 Count[mat, _?(Length[#] >= col &)]

nbrRows[mat, #] & /@ Range[10]

(* {10, 10, 10, 8, 5, 0, 0, 0, 0, 0} *)
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  • $\begingroup$ Thanks for your reply. $\endgroup$ – PoreyS Feb 10 at 18:03

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