Using App Designer, reading a numeric edit field and creating a double array from the inputs?

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Scotty Mac 2023-4-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1951288-using-app-designer-reading-a-numeric-edit-field-and-creating-a-double-array-from-the-inputs

评论： Stephen23 2023-4-23

I have 3 NumericEditFields and I enter 5700 & 4750 in the first 2 (the 3rd can be blank and thus only have an array with only 2 elements). I then convert them from MegaHertz to Hertz by the following:

       if isempty(app.NumericEditField_NotchCenterFreq1.Value)  % check to see if the field is empty first, if so, assign an empty string
                fc1 = {};
            else
                fc1 = app.NumericEditField_NotchCenterFreq1.Value;  
                fc1 = fc1 * 10e6;  % Convert to Hertz
            end
       if isempty(app.NumericEditField_NotchCenterFreq2.Value)
                fc2 = {};
            else
                fc2 = app.NumericEditField_NotchCenterFreq2.Value;  
                fc2 = fc2 * 10e6;  % Convert to Hertz
            end
            
            if isempty(app.NumericEditField_NotchCenterFreq3.Value)
                fc3 = {};
            else
                fc3 = app.NumericEditField_NotchCenterFreq3.Value;  
                fc3 = fc3 * 10e6;  % Convert to Hertz
            end
        % Create an array from entered inputs
            notch_fc=[fc1, fc2, fc3];
            make_loadset(app, notch_fc);

The notch_fc array is

notch_fc: 1×2 cell array =

[1×4 double] [1×4 double]

But I want it to be a double array (values for example)

notch_fc: 1x2 double =

1.0e+09 *

5.7000 4.7500

How can I accomplish this? I have searched and searched and can not find the answer. Thanks in advance!

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Answer 1

Stephen23 2023-4-22

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1951288-using-app-designer-reading-a-numeric-edit-field-and-creating-a-double-array-from-the-inputs#answer_1220878

编辑：Stephen23 2023-4-22

在 MATLAB Online 中打开

The reason why it is a cell array is because you told MATLAB to make a cell array. Basically you are doing this:

fc1 = 1;
fc2 = pi;
fc3 = {}; % if this is a cell array...
[fc1,fc2,fc3] % then so is this.
ans = 1×2 cell array
    {[1]}    {[3.1416]}

If any input to the concatenation operator is a cell array, then the output will be a cell array. This is explained here:

https://www.mathworks.com/help/matlab/matlab_prog/combining-cell-arrays-with-non-cell-arrays.html

https://www.mathworks.com/help/matlab/matlab_prog/valid-combinations-of-unlike-classes.html

Ergo, if you do not want a cell array output, do not provide cell arrays as the inputs.

"How can I accomplish this? I have searched and searched and can not find the answer."

If you want a numeric vector output then you need to provide numeric inputs. Note that numeric arrays cannot have "holes" in them, i.e. every element must contain some value. Some solutions:

output may change size: use empty numeric [].
output must remain same size: use NaN.

Lets try them both, right now:

fc3 = NaN; % numeric NaN
[fc1,fc2,fc3]
ans = 1×3
    1.0000    3.1416       NaN

or

fc3 = []; % numeric empty
[fc1,fc2,fc3]
ans = 1×2
    1.0000    3.1416

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Scotty Mac 2023-4-22

Thank you for the help! That helps alot. Much appreciated!

Stephen23 2023-4-23

@Scotty Mac: I am glad that it helped. Please remember to accept the answer that helped you!

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Using App Designer, reading a numeric edit field and creating a double array from the inputs?

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