Problem in plotting a summation

Question

Henry 2014-9-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/154153-problem-in-plotting-a-summation

编辑： Evan 2014-9-9

Hello everybody.

I'm having a serious problem in plotting a summation. My problem is the following: my function is (e^x)/x that is a multiplicative factor, outside the series, who multiplies the following series:

Sum for k = 1 to N of (k!)/(x^k)

I tried with

plot(plot::Sum(factorial(k)/2^k, k = 1..10)),

but the result is:

plot(plot::Sum(factorial(k)/2^k, k = 1..10)), plot(plot::Sum(factorial(k)/2^k, k = 1..10)), | Error: Unexpected MATLAB operator.

I don't understand what's the problem. I found this on your site but it doesn't work. Clearly, I wrote only the series without the multiplicative factor, to have an idea, but .. I don't know!!

Thanks to anyone will answer me!

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Joseph Cheng 2014-9-9

编辑：Joseph Cheng 2014-9-9

在 MATLAB Online 中打开

well plot(plot::Sum(factorial(k)/2^k, k = 1..10)) isn't in matlab syntax for starters.

**edit/update: this is with Mupad notation, not the first thing i think of when looking at matlab code.

which would be

plot(plot::Sum(k!/2^k, k = 1..10))

if you're looking to plot in MuPad.

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Answer 1

Evan 2014-9-9

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编辑：Evan 2014-9-9

Try out the cumsum function. Also it's worth noting that all the functions/operators you need (factorial, ./, .^, etc.) can all handle arrays, meaning you don't really need to worry about looping. You can create a single array that is each term of your cumulatively summed series using the factorial function and the element-by-element versions of the division and power operators, then plot that.

EDIT It looks like you're using MuPAD for this. My above explanation is for solving your problem using the standard MATLAB language.