Xlim error in App designer

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Mukesh
Mukesh 2025-3-22
编辑： VBBV 2025-3-27
% Value changing function: STARTKnob_2
function STARTKnob_2ValueChanging(app, event)
arguments
app
event.Value(1,1) {mustBeNumeric}=0
end
app.StartYear = event.Value;
if app.StartYear>app.StopYear-1 %checks the increasing-xrule
app.StopYear=min([app.StartYear+1,app.STOPKnob.Limits(2)]);
app.STOPKnob.Value=app.StopYear; %rotate the stop knob
app.StartYear=app.StopYear-1;
app.STARTKnob_2.Value=app.StartYear;
end
app.plotData();
end
% Value changing function: STOPKnob
function STOPKnobValueChanging(app, event)
arguments
app
event.Value(1,1) {mustBeNumeric}=0
end
app.StopYear = event.Value;
if app.StopYear<app.StartYear+1
app.StartYear=max([app.StopYear-1 app.STARTKnob_2.Limits(1)]);
app.STARTKnob_2.Value=app.StartYear;
app.StopYear=app.StartYear+1;
app.STOPKnob.Value=app.StopYear;
end
app.plotData();
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Mukesh
Mukesh 2025-3-25
移动：VBBV 2025-3-26
Thanks for all your help. I have figured out how it was initialised to same value. While setting the parameters for knob, the lower limit for both start & stop was set to 1850 by default. Thats why both had same value. Now i have created default function and sent the intital parameters accordingly and called it in startup function.
VBBV
VBBV 2025-3-26
编辑：VBBV 2025-3-27
@Mukesh if you dont want the default values of xlim to be used,
then inside the function plotData you need to put the xlim line with manual first which will override the default values.
function plotData(app)
xlim(app.UIAxes, 'manual') % put this line first
%app.StarYear.Value = event.Value
%app.StopYear.Value = event.Value
xlim(app.UIAxes, [app.StartYear.Value app.StopYear.Value])

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采纳的回答

Image Analyst
Image Analyst 2025-3-22
You need to debug your program. See
Debugging in MATLAB | Doug's MATLAB Video Tutorials
After that, when you see an error that says the limits of the min and max values you're passing into xlim must be increasing values, you'll know how to check their values. What you need to do is set a breakpoint at xlim and hover over app to see what the values of StartYear and StopYear are. Or else just put them in the code right before xlim
app.StartYear
app.StopYear % No semicolons!
xlim(app.UIAxes, [app.StartYear, app.StopYear])
What are their values?
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Image Analyst
Image Analyst 2025-3-23
编辑：Image Analyst 2025-3-23
So I assume that means you want the same start and stop values over multiple sets of data, instead of adjusting it on a vector-by-vector basis. But you're evidently setting them both to the same value.
Does your app have a startupFcn? If not, add one and set the app.Start and Stop to some default values. Or else use isempty() when you're trying to turn the knobs or plot data to make sure the start and stop values are not null.
Can you attach your GlobalTemp.mlapp so that I can fix it? Also a set of data if one is needed to run the program.
Mukesh
Mukesh 2025-3-25
Thanks for all your help. But I have figured out how it was initialised to same value. While setting the parameters for knob, the lower limit for both start & stop was set to 1850 by default. Thats why both had same value. Now i have created default function and sent the intital parameters accordingly and called it in startup function. But your debug idea helped a lot.

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更多回答（1 个）

Walter Roberson
Walter Roberson 2025-3-22
You do not provide initial values for app.StartYear or app.StopYear, so they are initialized to [] (the empty vector)
Then when you test
if app.StartYear>app.StopYear-1
then app.StartYear = event.Value might have given a value to app.StartYear, but app.StopYear is still [] and testing (Value>[]) is false.
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Walter Roberson
Walter Roberson 2025-3-23
It is not an error to calculate with [] .
(It is typically an error to try to store [] into indexed locations. Not always though.)
With it not being an error to calculate with [], the error is not encounted until the call to
xlim(app.UIAxes, [app.StartYear app.StopYear])
with app.StopYear being [] the above call would collapse to
xlim(app.UIAxes, [app.StartYear []])
which would be
xlim(app.UIAxes, app.StartYear)
which would error because the input vector is only length 1.
Mukesh
Mukesh 2025-3-23
Actually i have checked their value. I dont know how both variables are initialised to same value. So i understood why i was getting the error since it is not increasing numeric value input for xlim but now i am not gettting how how both variables are initialised to same value

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