Problems with indexing into an array with nan (indexing on 2 variables)

Hi All,

I'm having trouble using a logical variable ( Bandphase_logical = 9x5272240 logical) to find "true" events in another variable ( bandphase = 3x5272240 single). I think part of my problem is that the "bandphase" variable contains NaNs and I am trying to index over 2 different variables (see below).

"Bandphase_logical" contains 1's where an event occurs across a time series (5272240 samples). "bandphase" contains radian values across the entire timeseries (5272240 samples). Each row contains different frequency bands, and has a "NaN" where that sample does that have a frequency.

I'd like to do something along the lines of (I'd to create a loop where the bandphase variable changes adaptively with how many rows it has and same with the Bandphase_logical variable [e.g.: if bandphase had 5 rows and Bandphase_logical had 12 rows]):

bandphase(1,:)(Bandphase_logical(1,:)
bandphase(1,:)(Bandphase_logical(2,:)
.
.
bandphase(1,:)(Bandphase_logical(9,:)

bandphase(2,:)(Bandphase_logical(1,:)
bandphase(2,:)(Bandphase_logical(2,:)
.
.
bandphase(2,:)(Bandphase_logical(9,:)

bandphase(3,:)(Bandphase_logical(1,:)
bandphase(3,:)(Bandphase_logical(2,:)
.
.
bandphase(3,:)(Bandphase_logical(9,:)

I'd greatly appreciate any help! I'm thoroughly confused.

PK

Answer 1

[Stephen23]

for ii = 1:size(bandphase,1)
    for jj = 1:size(Bandphase_logical,1)
        tmp = bandphase(ii,:);
        tmp(Bandphase_logical(jj,:))
    end
end

To store the output (of different sizes) use a cell array:

S = [size(bandphase,1),size(Bandphase_logical,1)];
C = cell(S);
for ii = 1:S(1)
    for jj = 1:S(2)
        tmp = bandphase(ii,:);
        C{ii,jj} = tmp(Bandphase_logical(jj,:))
    end
end

You can download padcat to automatically pad with NaN's and create one numeric array:

mat = padcat(C{:})

[Walter Roberson]

No, you cannot have )( in MATLAB except for the case of indexing right after a dynamic field name.

[Stephen23]

@Walter Roberson: true, I missed that one! Thank you.

[Stephen23]

PAK's "Answer" moved here:

Hi Stephen and Walter,

This does work! I created a variable to store "tmp(Bandphase_logical(jj,:)). However, how do I make that variable ("phases") not overwrite with each iteration of jj (i.e.: so there are jj rows in "phases")? Each row of "phases" will be a different column length (e.g.: for jj = 1 it returns a 1x24 vector, for jj = 2 it returns 1x13 vector). I can't just do below, because the vectors are of different lengths.

phases(jj) = tmp(Bandphase_logical(jj,:))

Is there a way to place NaN to make the vector lengths the same as the matrix is getting populated?

Thank you again!

PK

[Stephen23]

@PAK: see my edited answer.

[PAK]

This was amazing. Thank you!!