Trouble plotting variables from cache menu and table

I created a table and assigned some variables to that table. I then created a drop down menu and called each one X and Y. This way I could just plot X and Y and I thought it would plot the variable at X and the variable at Y. It did not seem to work.

I got the error:

Error using matlab.ui.control.internal.model.ExactlyOneSelectionStrategy/validateValuePresentInItems (line 183)

'Value' must be an element defined in the 'Items' property.

Error in matlab.ui.control.internal.model.SelectedTextValueStrategy/validateValue (line 38)

value = obj.Component.SelectionStrategy.validateValuePresentInItems(newValue);

Error in matlab.ui.control.internal.model.AbstractStateComponent/set.Value (line 141)

value = obj.ValueStrategy.validateValue(newValue);

I added this to my properties:

Thrust = table2array(app.t(:,"Thrust")); % Both of these needs to be an element defined in
Time = table2array(app.t(:,"Time")); % the items property

Then I got the error:

Invalid default value for property 'Thrust' in class 'Appdesigner Name':

Unable to resolve the name app.t

The code that gave me the first problem:

  function PlotButtonPushed(app, event)
            Thrust = table2array(app.t(:,"Thrust"));
            Time = table2array(app.t(:,"Time"));
            app.XDropDown.Value = Thrust;
            app.YDropDown.Value = Time;
            X = app.XDropDown.Value;
            Y = app.YDropDown.Value;
           plot(app.UIAxes, X, Y);
           
           

The values from the table need to be opened first and it seems there is some kind of problem there.

The error pops up when I try to switch the variables in the cache menu or plot them.

I would like to define my variables as the values from my table and be able to choose which variables I want to plot. The values are a column of numbers.

Also, I was able to plot the values directly from the table, but that is not really user friendly and I am trying to plot the values using a cache menu to make it more user friendly. I did that with the below code:

           function PlotButtonPushed(app, event)
            Thrust = table2array(app.t(:,"Thrust"));
            Time = table2array(app.t(:,"Time"));
            plot(app.UIAxes, Time, Thrust)

Answer 1

[Srijith Kasaragod]

Hi,

I understand that you have a table consisting of multiple variables and you wish to have 2 dropdowns in the app, which selects variables from table to be plotted onto the UIAxes. Following is an example solution.

App contains two dropdowns, one button and a UIAxes. Three variables are declared to hold the table and dropdown values.

properties (Access = private)
    t; %variable to hold the table
    X; %variable to hold x-dropdown selection 
    Y; %variable to hold y-dropdown selection 
end

Startup function reads and saves the table into variable 't'. Using this table, x and y dropdowns are initialised to have all the variable names so that user can select which variables to plot.

function startupFcn(app)
    app.t= readtable("data.xlsx");
    app.XDropDown.Items=app.t.Properties.VariableNames;
    app.YDropDown.Items=app.t.Properties.VariableNames;
end

When dropdown values are changed, it is reflected in the variables 'X' and 'Y'.

% Value changed function: XDropDown
function XDropDownValueChanged(app, event)
    value = app.XDropDown.Value;
    app.X= value;
end

% Value changed function: YDropDown
function YDropDownValueChanged(app, event)
    value = app.YDropDown.Value;
    app.Y= value;
end

Once 'X' and 'Y' variables contain the values to be plotted, pushbutton callback function can plot them onto the UIAxes.

function PlotButtonPushed(app, event)
    app.X= app.t{:,app.XDropDown.Value};
    app.Y= app.t{:,app.YDropDown.Value};
    plot(app.UIAxes,app.X,app.Y);
end

Please refer 'uidropdown' documentation to know more about callback functions and assigning items of uidropdown.