Error using textscan Invalid file identifier Use fopen to generate a valid file identifier in app designer

I use a button to upload my "Data.txt" file and another button to calculate and plot it into UIaxes but im having error in "fid=fopen"

properties (Access = public)
        selectpath='';
    end
    
    % Callbacks that handle component events
    methods (Access = private)
        % Button pushed function: UploadButton
        function UploadButtonPushed(app, event)
            [file,path] = uigetfile('*.txt')
        end
        % Button pushed function: CalculateButton
        function CalculateButtonPushed(app, event)
fid=fopen(Data.txt(app.selectpath));
fclose(fid);                                    %Error using textscan 
                                                % Invalid file identifier. 
                                                % Use fopen to generate a valid file identifier.
seek=textscan(fid,'%f %f','headerlines',2);
g = cell2mat(seek);
x=g(:,1);
y=g(:,2);
[sortedX, sortIndex] = sort(x);
sortedY = y(sortIndex);
          sortedXLimit = sortedX(1:160,:);
          sortedYLimit = sortedY(1:160,:);
plot(app.UIAxes,value*peaks)                %for the graph
app.UIAxes.YLim = [0 205];

[darova]

I don't understand

Can you explain?

[sydney salvador]

I was trying to fix the porblem and saw that "fid" always highlighted but it always shows "Unrecognized method, property, or field 'path' for class 'testapp1'."

[sydney salvador]

I only understood that my upload button has stored the file as properties and my calculate button should get the file from properties and calculate it.

[darova]

Try this

[sydney salvador]

i has the same error

Answer 1

[Tommy]

It doesn't seem like your upload button stores anything. It saves the file and path into file and path and then exits, at which point the file and path are lost. This would work:

function UploadButtonPushed(app, event)
    [file,path] = uigetfile('*.txt');
    if file == 0
        % handle case where user clicks cancel
    else
        app.selectpath = fullfile(path, file);
    end
end

And then in your other callback:

function CalculateButtonPushed(app, event)
    fid=fopen(app.selectpath);
    seek=textscan(fid,'%f %f','headerlines',2);
    ...

[sydney salvador]

thank you

[sydney salvador]

plot(app.UIAxes,value*peaks)          
app.UIAxes.YLim = [0 205];

I have UI.axes placed in app designer and would like to know where to put this code to plot inside the axes

in my current code it is saying 'error'

[Tommy]

What is the error?

[sydney salvador]

Unrecognized function or variable 'value'.

[Tommy]

        function CalculateButtonPushed(app, event)
fid=fopen(Data.txt(app.selectpath));
seek=textscan(fid,'%f %f','headerlines',2);
g = cell2mat(seek);
x=g(:,1);
y=g(:,2);
[sortedX, sortIndex] = sort(x);
sortedY = y(sortIndex);
          sortedXLimit = sortedX(1:160,:);
          sortedYLimit = sortedY(1:160,:);
plot(app.UIAxes,value*peaks)                %for the graph
app.UIAxes.YLim = [0 205];

If this is your function, neither value nor peaks is defined before your call to plot. What should they equal? MATLAB doesn't have a clue.

[sydney salvador]

I assumed that i can replace "value" with "x" and "peaks" with "y" but an error occured

Error using *

Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the number of rows in the second matrix. To perform elementwise multiplication, use '.*'

I also used sortedXLimit & sortedYLimit but same error, my apologies for slow understanding I am self learning this for a year

[Tommy]

No worries! What exactly are you trying to plot? MATLAB interprets an asterisk * by itself as matrix multiplication, and matrix multipication A*B is only valid if A has the same number of columns as B has rows. Assuming x and y are both column vectors (with dimension Nx1 each), then x*y isn't valid as long as N != 1. If you want to multiply each element within x by the corresponding element within y, you can use element-wise multiplication, or x.*y. Note the period before the asterisk.

[sydney salvador]

my data is compiled in a ".txt" into 2 columns with nth rows i am trying to make the button "calculate" to process the data and plot it into Ui.axes the code within the button worked in normal matlab my problem is plotting it in app design

[Tommy]

Hmm... I'll assume you want to plot your sorted and trimmed y over your sorted and trimmed x, in which case you should try

plot(app.UIAxes,sortedXLimit,sortedYLimit)

If that's not what you want, could you provide the code which worked for you?

[sydney salvador]

Thank you sir it has worked now

Answer 2

[sydney salvador]

[sortedX, sortIndex] = sort(x);
sortedY = y(sortIndex);
          sortedXLimit = sortedX(1:160,:);
          sortedYLimit = sortedY(1:160,:);
           plot(app.UIAxes,sortedXLimit,sortedYLimit)          
           app.UIAxes.YLim = [0 1000];
           hold on
           findpeaks(sortedYLimit,sortedXLimit,'MinPeakProminence',205,'Annotate','extents')

sir my peaks arent showing on the graph on app designer, it shows in another window in matlab and when i use hold on it does not work

[Tommy]

At this point I'd recommend you open a new question. If you do so, post a link here and I'd be more than happy to take a look!

[sydney salvador]

here sir

https://www.mathworks.com/matlabcentral/answers/522269-peaks-of-plot-in-uiaxes-appdesigner-opening-in-another-window