# Extract Columns from Matrix [closed]

I want to extract columns 3 and 4 from the matrix below:

mat1=Table[{n, ksi,
r = c /. FindRoot[
SpheroidalS1[1, n, c, ksi], {c, BesselJZero[n + 1/2, 1]}
],
r*ksi},
{n, 4}, {ksi, {100, 250, 600, 950}}
] // Flatten[#, 1] & // Prepend[(Style[#, 14, Bold] & /@ {"n", "ksi", "c", "c*ksi"})] // Grid[#, Frame -> All] &

mat2=mat1[[3;;4,1;;16]]


But I get the following message:

Part::take: Cannot take positions 3 through 4 in Grid[Prepend[{n,ksi,c,c*ksi}][{{1,100,4.66544,466.544},<<14>>,{4,950,8.18302 -3.30575*10^-6 I,7773.87 -0.00314046 I}}],Frame->All]. >>

What gives?

## closed as off-topic by corey979, Feyre, Yves Klett, Bob Hanlon, m_goldbergOct 26 '16 at 20:15

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – corey979, Feyre, Yves Klett, Bob Hanlon, m_goldberg
If this question can be reworded to fit the rules in the help center, please edit the question.

• Replace // Grid with ;mat1//Grid in your code. Then run mat1[[All, 3 ;; 4]] – dan7geo Oct 26 '16 at 18:19
• More generally, never include the wrapper (e.g., Grid, Table, Row, Column) as part of the definition of the data. You can use parentheses to isolate the wrapper from the definition, e.g., (mat1 = ...)//Grid[#, Frame -> All] & – Bob Hanlon Oct 26 '16 at 18:24

the problem is mat1 is not a matrix or list, but a Grid. Your Table (with header row) appears as the first part of the Grid object, so you can do this:

 mat1[[1,All, 3 ;; 4]]


Note you also transposed the row/column order.

If you want to display that as a Grid : mat1[[1, All, 3 ;; 4]] // Grid[#, Frame -> All] &

Really you'd be better off to save the Table and only apply Grid when you want to display in formatted form. One way to do that is to add parenthesis to your code:

(  mat1 = Table[]... ) // Grid

• I don't get the desired results through: mat1[[1,All, 3 ;; 4]]. My results are {{1, 600, 4.4951, 2697.06}, {1, 950, 4.49248, 4267.86}}. Any suggestions? – George Giannoulis Oct 26 '16 at 19:02

I had to delete //Grid[#, Frame -> All] & and then as you suggested mat2 = mat1[[1, All, 3 ;; 4]]. Thank you all for your recommendations!

• With the headings mat1[[All, 3;;4]] or mat1[[All, {3,4}]]. Without the headings mat1[[2;;, 3;;4]] or mat1[[2;;, {3,4}]] – Bob Hanlon Oct 26 '16 at 19:20