Error using fprintf Unable to convert 'sym' value to 'double'.

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Sila Fundora 2020-9-30

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https://ww2.mathworks.cn/matlabcentral/answers/602257-error-using-fprintf-unable-to-convert-sym-value-to-double

评论： Star Strider 2020-10-7

采纳的回答： Star Strider

在 MATLAB Online 中打开

I am new in Matlab, and basically it seems I am not using the symbolic variables correctly.

t=0:0.5:10;sm x ;
R=zeros(1,length(t),'sym');
for ii=1:length(t)
    f=tanh(x)^2/(x^2)*cos((x*tanh(x))^(1/2)*t(ii));
       R(ii)=(2/pi)* int(f,x,0,inf);
fprintf('%2.1f\t  %3.10f\n',[t(ii); R(ii)])
end

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采纳的回答

Star Strider 2020-9-30

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/602257-error-using-fprintf-unable-to-convert-sym-value-to-double#answer_502654

在 MATLAB Online 中打开

If you have R2016b or later, use vpaintegral:

This works (with the fprintf call corrected to eliminate the spaces between the backslant and the characters they escape, and a few other corrections):

t = 0: 0.5: 10;
syms x;
R = zeros (1, length (t),'sym');
for ii = 1: length (t)
    f = tanh (x) ^ 2 / (x ^ 2) * cos ((x * tanh (x)) ^ (1/2) * t (ii));
    R (ii) = (2 / pi) * vpaintegral (f, x, 0, inf);
    fprintf ('% 2.1f \t% 3.10f \n', [t (ii); R (ii)])
end