Can't store values into array MATLAB

Question

I have a 1x280 structure in Matlab. In order for me to use the values, I changed it to struct2cell array.

An example of how one of the structures among the 280 looks is below :

Field       Value               Min       Max

point1      [29,469]            29        469
point2      [42,469]            42        469
-------------------------------------------

After changing to a cell array using the below code:

showlines = struct(lines);
cellData = struct2cell(showlines);


cellData{1,1}(1) 
    = 29

However, if I use this :

cellData{1,1:280}(1);

There is an error

Error:: bad cell reference operation

I would need to keep all the x values of point1 in each of the 280 structures into an array so as to find out the maximum X value of point1 in them. Any idea how to do it?

Thank you very much in advance.

Rody Oldenhuis · Accepted Answer · 2012-08-30 14:32:31Z

1

Although not a direct answer to your question, you might be interested to know that

%# some example data
S(1).point1 = [29 469];
S(1).point2 = [42 469];

S(2).point1 = [30 470];
S(2).point2 = [43 470];

...

S(280).point1 = [130 870];
S(280).point2 = [243 970];

%# transform to regular array
pt1 = reshape([S.point1],[],2).';
pt2 = reshape([S.point2],[],2).';

will result in

pt1 = [29   469       pt2 = [42   469
       30   470              43   470
       ...                   ... 
       130  870];            243  970];

which enables you to do things like

>> pt1(:, 2)
ans = 
    469
    470
    ..
    870

>> min(pt1(:,1))
ans = 
    29

Does that solve your problem?

To any passers by: what is the notation [S.field] for non-scalar structs called? Does it even have a name? Questions involving this technique frequently pop-up, and it would help if I knew what it's called so I can post a link to the manual page in the answer...

edited Aug 30, 2012 at 14:32

answered Aug 30, 2012 at 13:56

Rody Oldenhuis

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6 Comments

Melvyn Over a year ago

Yes, that solves my problem if I have only S(1) to S(3) or so. However in my case there is 280 'S' due to my structure having 280 of that. How do I go about filling those S(3) to S(280) point1 and point 2 automatticaly? Thanks

Rody Oldenhuis Over a year ago

@Melvyn my answer just gives an example. The same line (i.e., [S.point1]) will work perfectly fine even when S contains a billion values. Did you try the above on your own structure?

Melvyn Over a year ago

sorry, so do I change "S" into my own cell array name? I.E after struct2cell, i renamed the cell array as "cellData". This array has 280 point1 and point2. So do I write [cellData.point1]?

Doresoom Over a year ago

@RodyOldenhuis You might have some memory problems with a billion values. :)

Rody Oldenhuis Over a year ago

@Doresoom conceptually speaking, of course :) BTW, 1e9 values is about 8GB == no problem at all on my machine :p

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