Extract columns and rows from matrix

I need to extract a column (let's say 1st) from 1st matrix (5x5) to use it as a row (let's say 5th) in a 2nd matrix (5x5).

Thanks in advance

Answer 1

[Torsten]

first = rand(5)

first = 5×5

0.6556 0.1094 0.2522 0.5119 0.5134 0.4183 0.3149 0.5010 0.4793 0.0783 0.9219 0.1391 0.7669 0.4079 0.2564 0.3306 0.2384 0.4618 0.3429 0.0067 0.3400 0.3090 0.4482 0.6066 0.5850

second = rand(5)

second = 5×5

0.7720 0.9819 0.2196 0.4291 0.6845 0.8561 0.0148 0.9716 0.8685 0.8155 0.3618 0.2091 0.7744 0.6708 0.5010 0.1139 0.4576 0.3263 0.4784 0.1249 0.3806 0.5838 0.4502 0.5900 0.5781

second(5,:) = first(:,1).'

second = 5×5

0.7720 0.9819 0.2196 0.4291 0.6845 0.8561 0.0148 0.9716 0.8685 0.8155 0.3618 0.2091 0.7744 0.6708 0.5010 0.1139 0.4576 0.3263 0.4784 0.1249 0.6556 0.4183 0.9219 0.3306 0.3400

[Heorhii]

Much appreciated!!

[Stephen23]

Note that the TRANSPOSE is optional:

first = rand(5)

first = 5×5

0.2622 0.9271 0.8045 0.4209 0.9297 0.1965 0.1722 0.4752 0.5092 0.2747 0.5255 0.8954 0.8495 0.5751 0.1948 0.5142 0.3306 0.3673 0.1700 0.1440 0.1852 0.6967 0.2868 0.3201 0.3975

second = rand(5)

second = 5×5

0.0998 0.1903 0.2646 0.7202 0.6271 0.3664 0.1022 0.9504 0.5349 0.1289 0.7642 0.0478 0.2630 0.9633 0.7535 0.5964 0.9338 0.9450 0.4532 0.1578 0.8699 0.7766 0.4579 0.5648 0.2570

second(5,:) = first(:,1)

second = 5×5

0.0998 0.1903 0.2646 0.7202 0.6271 0.3664 0.1022 0.9504 0.5349 0.1289 0.7642 0.0478 0.2630 0.9633 0.7535 0.5964 0.9338 0.9450 0.4532 0.1578 0.2622 0.1965 0.5255 0.5142 0.1852

[Torsten]

Interesting that MATLAB doesn't differ between row and column in this case. Why is it ?

[madhan ravi]

@Torsten that is because the number of elements in L.H.S is equal to the R.H.S

[Dyuman Joshi]

@madhan ravi, then this should work as well, but it doesn't.

y = rand(5,5)

y = 5×5

0.2054 0.3064 0.3352 0.1937 0.8819 0.9259 0.3211 0.8781 0.5697 0.8578 0.3453 0.2379 0.6059 0.2627 0.2939 0.5965 0.9375 0.1124 0.3127 0.4328 0.2790 0.7215 0.9603 0.4169 0.3628

y([2 3], :) = y(:, [2 3])

Unable to perform assignment because the size of the left side is 2-by-5 and the size of the right side is 5-by-2.

[Dyuman Joshi]

@Torsten

An explaination (or definition) is provided in the documentation of subsasgn -

For multidimensional arrays, A(i,j,k,…) = B assigns B to the specified elements of A. B must be length(i)-by-length(j)-by-length(k)-… or be shiftable to that size by adding or removing singleton dimensions.

1xN is shiftable to Nx1 by removing the 1st singleton dimesion.

1xN == 1xNx1 -> Nx1

[Torsten]

Thank you for the explanation.