How to display error using error function?

Question

Porgs 2018-5-1

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https://ww2.mathworks.cn/matlabcentral/answers/398336-how-to-display-error-using-error-function

评论： Walter Roberson 2019-8-12

I have a program that computes thermal conductivity based on an input of a certain alloy and temperature. I would like to have the function display an error if the wrong alloy is inputted. Would It be possible to do this with the error function? This is the code I have so far.

function k = ThCond(alloy,T) % T = input temperature
k = zeros(1,numel(T));
for a = 1:numel(T)
      if (298 <= T(a)) && (T(a) <= 840) && strcmp(alloy,'Al2')
         k(a) = 149.7 + 0.0809.*T(a) - (1.*10^(-4)).*(T(a).^2);
        elseif (298 <= T(a)) && (T(a) <= 773)
           k(a) = 76.64 + 0.2633.*T(a) - (2.*10^(-4)).*(T(a)^2);
        end
        if (293 <= T(a)) && (T(a) <= 890) && strcmp(alloy,'Al3')
            k(a) = 124.7 + 0.56.*T(a) + (1*10^(-5)).*(T(a)^2);
        end
        if (100 <= T(a)) && (T(a) <= 1200) && strcmp(alloy,'Cu1')
            k(a) = 453.9 - 0.1054.*T(a);
        end
        if (460 <= T(a)) && (T(a) <= 1188) && strcmp(alloy,'Cu2')
            k(a) = 140.62 + (112.14.*10^(-4)).*T(a);
        end
        if  T(a) <= 1443 && strcmp(alloy,'Cu3')
            k(a) = 16.041 + (438.9.*10^(-4)).*T(a);
        end
        if (400 <= T(a)) && (T(a) <= 1000) && strcmp(alloy,'St1')
            k(a) = 76.63 - 0.0459.*T(a);
        end
        if (298 < T(a)) && (T(a) < 1573) && strcmp(alloy,'St2')
            k(a) = 6.31 + ((27.2.*10^(-3)).*T(a)) - (7.*10^(-6)).*(T(a).^2);
        end
        if  T(a) <= 1727 && strcmp(alloy,'St3')
            k(a) = 20 + (61.5.*10^(-4)).*T(a);
        end  
  end
  end

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Porgs 2018-5-1

Not really, I would like to use the error fuction to display a personal error message that I write, to the user.

Walter Roberson 2018-5-1

在 MATLAB Online 中打开

error('Alloy must be H2SO4 or CuTi2C6H8') ;

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Answer 1

Wick 2018-5-1

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在 MATLAB Online 中打开

Simple enough then.

err = 'This is an error message.'; % perhaps something a bit more descriptive
error(err);

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Answer 2

Porgs 2018-5-1

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https://ww2.mathworks.cn/matlabcentral/answers/398336-how-to-display-error-using-error-function#answer_318116

Where would I put that in my code because I'm getting an error message when I'm trying to use this.

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Wick 2018-5-1

That's literally what the 'error' function does. It displays an error and breaks execution (unless it's part of a try,catch structure). So you'd put it as the result of an 'else' statement or possibly as result of an 'otherwise' option in a switch,case structure.

If you you don't want an actual error message and just want text displayed to the screen you can use the 'disp' or 'warning' commands instead.

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