App Designer returning Value in EditField

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I wrote a code to calculate some values I insert in the Edit fields.
First of all do I have a DropDown Menu, with some values which I want to calculate with.
After I performe the calculation (with the value from DropDownMenu and values from EditField) do I want to return the result in an Edit field.
If run the programm and Insert all my values do I get the following error:
"Error using matlab.ui.control.internal.model.AbstractNumericComponent/set.Value (line 111)
'Value' must be a double scalar."
That's my code for the DropDown menu. I want to safe the value in the variable "app.d_th"
% Value changed function: aDropDown
function aDropDownValueChanged(app, event)
app.d_th = app.aDropDown.Value
I have a Calculation Button which looks like this. I have shortened the entire calculation. that's just to show you how it looks. The goal is when I press the Button I want to performe the calculation and display it in the "ResultEditField"
% Value changed function: BerechnenButton
function BerechnenButtonValueChanged(app, event)
value = app.BerechnenButton.Value;
d_th = app.d_th/1000 %in meter. 3.6mm = 0.0036m
p_h = app.p_h * 10^5 %Hochdruck in pascal
m_flow = d_th.^2 + p_h
app.ResultEditField.Value = m_flow
Any hints?

Accepted Answer

Mario Malic
Mario Malic on 8 Mar 2021
Edited: Mario Malic on 8 Mar 2021
app.aDropDown.Value is one of the values in Items (if ItemsData is empty), therefore it's a character array.
if you set ItemsData as well to be numeric, then Value property will be of the same type. However, you can keep it simple and use line below to fix the issue.
app.d_th = str2num(app.aDropDown.Value)
Giancarlo Meccariello
Giancarlo Meccariello on 8 Mar 2021
I started again with the programm and checked every step.
I found the problem, the only mistake was the missing conversion str2num!
Everything fine now!

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