Series summation issue - conversion to double error

Question

Jon 2013-2-20

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/64328-series-summation-issue-conversion-to-double-error

Hi, I'm trying to write a series summation code and I'm getting the "conversion to double" error when I plot.

Here's the part of the code with trouble:

syms m
rhs = (1./(1+(2.*(t- m.*p))./tc)).* exp((-2.*r^2)./(r^2.*(1+ (2.*(t-m.*p)./tc))));
summation1 = symsum(rhs,0,1.89E5);

Where tc, r, and p are constants and t is a timespace with 36 spaces.

Is the problem that I'm asking it to sum from 0 to 1.89e5 with those 36 time spaces?

Thanks

EDIT: http://i.imgur.com/mz2KV5h.jpg Link is of the sum

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Answer 1

bym 2013-2-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/64328-series-summation-issue-conversion-to-double-error#answer_75923

在 MATLAB Online 中打开

At some point, Matlab gives up & returns the indefinite summation. You can try this:

clc;clear
syms m
tc = 3;
p = 3;
t = 1:10;
r =2;
rhs = (1./(1+(2.*(t- m.*p))./tc)).* exp((-2.*r^2)./(r^2.*(1+ (2.*(t-m.*p)./tc))));
summation1 = symsum(rhs);
f = matlabFunction(summation1);
f(189000)
f(10)
ans =
    1.0e-005 *
    Columns 1 through 8
     -0.2646   -0.2646   -0.2646   -0.2646   -0.2646   -0.2646   -0.2646   -0.2646
    Columns 9 through 10
     -0.2646   -0.2646
ans =
    Columns 1 through 8
     -0.0608   -0.0634   -0.0662   -0.0692   -0.0725   -0.0762   -0.0802   -0.0847
    Columns 9 through 10
     -0.0897   -0.0954