Error with selecting data in 3D matrix

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Sam
Sam 2015-1-3
编辑： dpb 2015-1-4
I have a 3D matrix. The first dimension contains all datapoints (of markers, forces, moments,...), the second contains all the headers/names (of the markers, forces, moments,...) and the third dimension contains the x, y or z-coordinates. (x = 1, y = 2, z = 3).
I want to select all the datapoints for the MARKERS only (x-coordinates):
VideoSignals(:,1:strcmpi('*13', data_stair_rise(1,1).VideoSignals_headers),1)
So first I put ':' to select all the datapoints, but then I need to select ONLY the markers: they go from '1' to '*13' and last I select the x-coordinates using '1'.
It gives an error probably because of a wrong use of brackets I suppose. I tried several things... Help?
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Sam
Sam 2015-1-3
The second dimensions contains strings. It contains 1 row and (for example) 220 columns. I need to select all the markers for 5 subjects. I have noticed in my headers, that the 'markers' and the 'forces' (in the second dimension) are seperated by a string '*136' or '*137' or '*138' or '*139'. So I thought I could use 'strcmpi' to say to the computer that he should take the columns going from '1' tot the strcmpi '*13'-column.
dpb
dpb 2015-1-3
编辑：dpb 2015-1-4
We need SPECIFICS, not generalizations and what you "thought"...
Give an example of the data you're trying to parse.
Presumimg VideoSignals is an array and not a function, then the expression
VideoSignals(:,1:_something_,1)
is an addressing expression that addresses all rows (the first ':') by columns of some vector 1 thru whatever the something expression evaluates to over the first plane.
strcmpi will return a vector of T:F where the comparison succeeds or fails in the vector given it. Thus you've written (presuming the strcmpi call even works) an addressing expression like
VideoSignals(:,1:[T F F F ... T ...],1)
This clearly isn't valid Matlab syntax as written so it won't be even if obfuscated by not having a variable to store the result of the function call into and use...
Think first, type later...
ADDENDUM
VideoSignals(:,1:[T F F F ... T ...],1) ... isn't valid Matlab syntax ...
But, if it really is what you're looking for,
VideoSignals(:,[T F F F ... T ...],1)
could be if the logical vector is of the right dimension and the assignment is written correctly so number elements of LHS is same as those of RHS.

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