Cell Array storing RGB

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SG 2015-5-15

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评论： SG 2015-5-15

采纳的回答： Walter Roberson

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I am storing color short names in a cell array as follows:

color{i,j} = 'r';

Then I'd like to use this cell array to set the color properties of some texts as follows:

   text('String', d{i,j},'Units', 'Points',...
        'FontSize', 8, 'HorizontalAlignment', 'right', ...
        'Color', color(i,j));

However, I get the error "Color value must be a 3 element numeric vector". I have tried using a function that convert the short name of colors to their RGB triplet, but it seems that color(i,j) does not output a string/char. How should I go about this? Thank you.

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Answer 1

Walter Roberson 2015-5-15

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If you are doing one at a time, then color{i,j} gets to the character.

If you were trying to do a whole bunch of them, such as to name the colors for each point of scatter3, then a lookup table is probably easiest.

RGBtab = [0 0 1; 0 1 0; 0 0 0; 1 0 0];  %RGB codes for colors
colorabbr = {'b', 'g', 'k', 'r'};  %must match order of RGB triple rows
[tf, idx] = ismember(color(:), colorabbr); %look up codes to find index
colorrgb = RGBtab(idx,:);  %convert to RGB triples

and now colorrgb would be an N x 3 of RGB. If you needed to you could

reshape(colorrgb, size(color,1), size(color,2), 3)

to get a truecolor array

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SG 2015-5-15

Wow that works perfectly. Thank you.

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Answer 2

Image Analyst 2015-5-15

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That should work except that you used parentheses which gives the whole cell, rather than braces, which gives the contents of the cell.

color(i,j) = a cell, the cell in the ith row, jth column of the cell array called color.

color{i,j} = the CONTENTS OF the cell at row i, column j

Try this:

text('String', d{i,j},'Units', 'Points',...
        'FontSize', 8, 'HorizontalAlignment', 'right', ...
        'Color', color{i,j});  % use braces instead of parentheses.