Function 'datenum' not supported for code generation. Function 'MATLAB Function'

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Seema Borase
Seema Borase on 20 Jun 2020
Commented: Steven Lord on 10 Dec 2021
The following picture is a part of the Simulink model and I use the MATLAB Fcn (Library function) to call the datenum function.
functiontime = funcPlotGraph(xAxis, yAxis, timeperiod1, timeperiod2)
legendsCol = {};
dim = 2;
% Convert long tick time to DateTime
time = datetime(datestr(xAxis/86400000 + datenum(1970,1,1)));
% plot graph between time vs yAxis
plot(xAxis, yAxis);
legendsCol{end+1} = 'Actual';
hold on
if ~isequal(timeperiod1, '0')
% average
movingAve = movmean(yAxis, timeperiod1);
plot(time, movingAve);
legendsCol{end+1} = 'Avg';
end
if ~isequal(timeperiod2, '0')
% average
movingAve20 = movmean(yAxis,timeperiod2);
plot(time, movingAve20);
legendsCol{end+1} = 'Avg 2';
I'm getting the following error while compiling the model:
Function 'datenum' not supported for code generation. Function 'MATLAB Function' (#88.184.201), line 5, column 43: "datenum(1970,1,1)" Launch diagnostic report.
Component:MATLAB Function | Category:Coder error
Simulink does not have enough information to determine output sizes for this block. If you think the errors below are inaccurate, try specifying types for the block inputs and/or sizes for the block outputs.
Component:MATLAB Function | Category:Coder error
Undefined function or variable 'time'. The first assignment to a local variable determines its class. Function 'MATLAB Function' (#88.409.413), line 15, column 14: "time" Launch diagnostic report.
Component:MATLAB Function | Category:Coder error
Undefined function or variable 'time'. The first assignment to a local variable determines its class. Function 'MATLAB Function' (#88.558.562), line 22, column 8: "time" Launch diagnostic report.
Component:MATLAB Function | Category:Coder error
Errors occurred during parsing of MATLAB function 'TestMatlabModelOld/MATLAB Function'
Component:MATLAB Function | Category:Coder error
Simulink cannot determine sizes and/or types of the outputs for block 'TestMatlabModelOld/MATLAB Function' due to errors in the block body, or limitations of the underlying analysis. The errors might be inaccurate. Fix the indicated errors, or explicitly specify sizes and/or types for all block outputs.
Component:MATLAB Function | Category:Coder error
Simulink cannot determine sizes and/or types of the outputs for block 'TestMatlabModelOld/MATLAB Function' due to errors in the block body, or limitations of the underlying analysis. The errors might be inaccurate. Fix the indicated errors, or explicitly specify sizes and/or types for all block outputs.
Component:Simulink | Category:Model error

Answers (1)

Siddharth Bhutiya
Siddharth Bhutiya on 22 Oct 2020
Edited: Siddharth Bhutiya on 22 Oct 2020
As the error indicates, datenum is not supported for code generation. However, datetime does support code generation and it is recommended to use datetime over datenum, even when not doing code generation.
Is there a specific reason you are trying to use datenum over datetime ?
  2 Comments
Steven Lord
Steven Lord on 10 Dec 2021
Let's get a sample date number.
n = datetime('now') % Use for comparison later
n = datetime
10-Dec-2021 14:05:23
d = datenum(n)
d = 7.3850e+05
Now to convert d back into a datetime like n, call datetime with the 'ConvertFrom' name-value pair argument.
n2 = datetime(d, 'ConvertFrom', 'datenum')
n2 = datetime
10-Dec-2021 14:05:23
I believe this syntax is supported for code generation.

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