Matlab filter columns of array based on value in row

I have a 3 x 3000 array with x, y, z as the rows.

I want a new array from filtering the above if z == 3.

I tried

```

task3_xy = xy_arr(~ismember(xy_arr(3, :), [3]),:);

```

but it's telling me

The logical indices in position 1 contain a true value outside of

the array bounds.

How else can I do this?

Answer 1

[Arif Hoq]

use 'find' function to look up the value which is equal to 3 in 'z'

x=randi(100,3,3000);
y=randi(80,3,3000);
z=randi(50,3,3000)

z = 3×3000

35 8 45 3 21 6 11 1 25 14 2 45 43 47 29 20 38 46 48 21 9 24 50 30 24 17 35 9 16 5 4 31 34 37 50 31 38 47 22 12 3 9 6 25 12 19 16 6 30 40 31 42 19 21 24 37 3 43 3 21 16 48 19 3 32 24 27 10 37 7 36 26 13 10 25 40 43 50 2 46 22 3 50 43 46 1 43 14 9 9

Idx_New_array=find(z==3)  % index value of z whihc is equal to 0

Idx_New_array = 179×1

10 12 32 66 80 86 156 194 270 349

if you want to find the row and column

[row col]=find(z==3)

row = 179×1

1 3 2 3 2 2 3 2 3 1

col = 179×1

4 4 11 22 27 29 52 65 90 117

is that your expectation or you want to replace the index value of z ?

Answer 2

[Nobutaka Kim]

I can do it in a multi-step process

```

xy_arr = [x; y; task_num];

xy_logical_arr = (xy_arr(3, :)==3);

job_xy = xy_arr(:, xy_logical_arr);

```