Fplot warnings, fails on array input.

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Rasmus Svendsen 2016-5-31

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https://ww2.mathworks.cn/matlabcentral/answers/286586-fplot-warnings-fails-on-array-input

评论： Walter Roberson 2016-6-3

Hello. I'm new to Matlab. I just got a new PC, and now getting warnings using fplot. I cant find out whats wrong. The plot shows up, but i dont know how the warnings effects the plot.

Does anyone know what to do?

Thnaks

    >> c = @(T) 0.0002374*T^3-0.05304*T^2+4.591*T+1450.59;
fplot(c,[2 30])
grid
title('Lydhastighed i havvand (dybde = 100 m, saltindhold = 3,5 pct)')
xlabel('Temperatur (grader C)')
ylabel('Lydhastighed (m/s)')
Warning: Function fails on array inputs. Use element-wise operators to increase speed. 
> In matlab.graphics.function.FunctionLine>getFunction
  In matlab.graphics.function.FunctionLine/set.Function_I
  In matlab.graphics.function.FunctionLine/set.Function
  In matlab.graphics.function.FunctionLine
  In fplot>singleFplot (line 223)
  In fplot>@(f)singleFplot(cax,{f},limits,extraOpts,args) (line 182)
  In fplot>vectorizeFplot (line 182)
  In fplot (line 153)

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Rohit Reddy Madasani 2016-6-3

Hi Rasmus,

The warning clearly indicates that the operators involved in computing "c" are not element-wise operators. These warnings can be avoided by replacing the operators * and ^ with element-wise operators .* and .^ respectively.

c = @(T) 0.0002374.*T.^3-0.05304.*T.^2+4.591.*T+1450.59;

More information on array vs matrix operations can be found in the below link:

http://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html