Can't get data from input string

Question

Vilde Solberg 2021-6-22

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/862365-can-t-get-data-from-input-string

评论： Vilde Solberg 2021-6-24

Hi! I have gotten a data file which contains 57 different "keys" like 'XPOS' (x-position), YPOS (y-position), etc. Within these "keys" the data is stored in arrays. I want to ask the user "which dataset do you want to work with" and thus use this input in further calcualtions. I approached this in the same way I would in Python, but I have not gotten a usable result. My current code is attached.

For information, I would like the user to write "XPOS" as input.

The error I get is at the bottom of the code.

Thank you in advance!

data = load('x.mat');
name = input('Which dataset do you wanna work with?   ','s');
if isempty(name)
    reply = 'Y';
end
pos = data.name;
plot(data.Time,pos);        %Just a simple plot of position against time
%%%%%%     Mean, max, min calc     %%%%%%
Mean = mean(pos);
Max = max(pos);
Min = min(pos);
Column = [['Max_ : ',  num2str(Max)];['Min_ : ',  num2str(Min)];['Mean : ', num2str(Mean)]];
disp(Column);
%%% MY ERROR %%%
Reference to non-existent field 'name'.
Error in plotter (line 20)
pos = data.name;

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Answer 1

Walter Roberson 2021-6-22

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/862365-can-t-get-data-from-input-string#answer_730525

在 MATLAB Online 中打开

if ~isfield(data, 'name')
   error('dataset "%s" is not loaded', name)
end
pos = data.(name);

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Walter Roberson 2021-6-24

编辑：Walter Roberson 2021-6-24

在 MATLAB Online 中打开

if ~isfield(data, name)
   error('dataset "%s" is not loaded', name)
end
pos = data.(name);

If data.XPOS works but name = 'XPOS'; data.(name) does not work, then please show

fn = fieldnames(data);
if ismember(name, fn)
    fprintf('field "%s" IS found as a field name\n', name);
else
    fprintf('field "%s" is NOT found as a field name\n\n', name);
    for K = 1 : length(fn)
       thisfield = fn{K};
       fprintf('field #%d is %d characters long "%s". chars are: ', K, length(thisfield), thisfield);
       fprintf('%s\n\n', mat2str(double(thisfield)));
    end
end

This is intended as debugging code. It might, for example, help you through a situation where the stored field name turns out to be XP0S instead of XPOS

Vilde Solberg 2021-6-24