Index matrix changing values outside index to NaN

I have an index matrix that is 480x1 in size with values ranging from 1 to 267, and I have a data matrix that is 261x1 in size. I need to multiple the two, or use the index matrix to index the data matrix resulting in a 480x1 matrix. The issue is that i cannot do so because some of the values in the index exceed the range of rows available in the data matrix (i.e., 262) and I cannot remove rows in the index exceeding the range of rows in the data matrix, because I ultimately need a resulting 480x1 data structure.

Is there a way to have a resulting 480x1 data structure where values in the index matrix that exceeded the range of rows in the data matrix are replaced by zeros or NaN?

Let's say for a simplified example I had:

Idx = [1,2,3,4,9,5,6,7] '

data = [1.5, 4.2, 3.4, 5.6, 7.8, 6.2, 7.5, 5.2]'

I'll get an error if I do result = idx(data) due to the index exceeding the dimensions of the data matrix, is there a way to get a result such as:

result = [1.5, 4.2, 3.4, 5.6, NaN, 7.8, 6.2, 7.5]

Answer 1

[Voss]

idx = [1,2,3,4,9,5,6,7]'

idx = 8×1

1 2 3 4 9 5 6 7

data = [1.5, 4.2, 3.4, 5.6, 7.8, 6.2, 7.5, 5.2]'

data = 8×1

1.5000 4.2000 3.4000 5.6000 7.8000 6.2000 7.5000 5.2000

ND = numel(data)

ND = 8

result = NaN(size(idx))

result = 8×1

NaN NaN NaN NaN NaN NaN NaN NaN

is_good_idx = idx <= ND

is_good_idx = 8×1 logical array
   1
   1
   1
   1
   0
   1
   1
   1

result(is_good_idx) = data(idx(is_good_idx))

result = 8×1

1.5000 4.2000 3.4000 5.6000 NaN 7.8000 6.2000 7.5000

[Mackenzie Taylor]

Thank you so much! This works.