Merging row elements into single numbers

If you have the 3*3 matrix

C = [3 4 5
    6 7 9
    1 5 8]

and you want to change it to the 3*1 matrix

C = [345
    679
    158] 

so that you can for example sort it in descending order of the rows, how would you do this? Thank you.

Answer 1

[Chris]

Edit: Use Star Strider's answer. It's faster.

C = [3 4 5
    6 7 9
    1 5 8]

C = 3×3

3 4 5 6 7 9 1 5 8

C = double(string(C).join(''))

C = 3×1

345 679 158

[Chris]

Breaking it down:

C = [3 4 5
    6 7 9
    1 5 8] % The matrix

C = 3×3

3 4 5 6 7 9 1 5 8

string(C) % String arrays are nice to work with

ans = 3×3 string array
    "3"    "4"    "5"
    "6"    "7"    "9"
    "1"    "5"    "8"

string(C).join('') % Mush the strings together with no delimiter between

ans = 3×1 string array
    "345"
    "679"
    "158"

C = double(string(C).join('')) % Cast the output back into a double array

C = 3×1

345 679 158

[Star Strider]

Another approach —

C = [3 4 5
    6 7 9
    1 5 8]

C = 3×3

3 4 5 6 7 9 1 5 8

C*10.^[2;1;0]

ans = 3×1

345 679 158

Just thought I’d add that for fun!

.

[Chris]

Interesting. This was probably the most obvious method before strings? Easily generalized for an array of single-digit integers:

C*10.^[size(C,2)-1:-1:0]'