str2num not working on array

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Nikolay N Valov
Nikolay N Valov 2019-9-18
编辑： Stephen23 2019-9-19
So the main issue is that when I used inputdlg and put in my desired color, str2num does not read it. I have tried str2double which produces a NaN which makes sense. I am not sure how to circumvent this issue.
%initialize colors
Grey = [0.5 0.5 0.5];
Red = [1 0 0];
Blue = [ 0 1 0];
Green = [ 0 0 1];
%prompt details of simulation
screenXpixels = 1920;
screenYpixels = 1080;
baseRect = [0 0 200 200];
prompt = {'Enter Arc Color (Grey, Red, Green, Blue):','Enter Arc Radius:','Enter Arc Angle','Enter amplitude constant:','Enter Frequency of Oscillation'};
dlgtitle = 'OscillatingDotDemo';
answer = inputdlg(prompt,dlgtitle);
arcColor = str2num(answer{1,1});
...
So when I run this, it returns an empty array.
  1 个评论
Adam
Adam 2019-9-18
str2num will convert e.g. '7' (char) to 7 (double), it doesn't have magic properties to interpret anything beyond that though, such as converting a colour string to a colour rgb or the index into a list of colour strings.

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回答（2 个）

Star Strider
Star Strider 2019-9-18
It returns an empty array because you apparently ask for a character array (for example ‘Red’) as the first input. That is not a number. If you enter a number instead of a color, it will return that number.
Stephen23
Stephen23 2019-9-19
编辑：Stephen23 2019-9-19
It would be simpler to use a structure (in this example I entered "Red" into the dialog box):
>> S.red = [1,0,0];
>> S.green = [0,1,0];
>> S.blue = [0,0,1];
>> S.gray = [1,1,1]*0.5;
>> S.(lower(answer{1}))
ans =
1 0 0
https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

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