Help to transform math formula to matlab

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Matthew Lima
Matthew Lima 2021-11-14
评论： Dave B 2021-11-15
Hello,
I am trying to transform this formula into matlab, but I can't use a for/while loop. X is an array with dimension n and every position receives this sum.
I tried like this, but I couldn't remove the loop here, can I achieve this without a loop?
I also tried to use arrayfun, but without success because every position of the array was receiving the same value.
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Matthew Lima
Matthew Lima 2021-11-14
Thank you so much Dave, I am new to Matlab i didn't realize how simple it is.
Thank's for the clear explanation.
Dave B
Dave B 2021-11-14
编辑：Dave B 2021-11-15
Ah I was trying to avoid doing it for you so that you could feel the satisfaction :) Glad it feels simple, hope it stays that way as you delve deeper!
note this is the simplified version of what you wrote:
x = log(1:n) * sum(exp((1:m).^2))

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回答（1 个）

Sulaymon Eshkabilov
Sulaymon Eshkabilov 2021-11-15
Ran in:
Using the vectorization:
format long
m=5;
jj=1:m;
XSum1 = sum(log(jj).*exp(jj.^2))
XSum1 =
1.158997425794889e+11
% Or alternatively
Xs = log(jj).*exp(jj.^2);
XSum2=sum(Xs)
XSum2 =
1.158997425794889e+11
% Sum stepby-step:
cumsum(Xs)
ans = 1×5
1.0e+11 * 0 0.000000000378446 0.000000089399921 0.000123277048990 1.158997425794889
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Dave B
Dave B 2021-11-15
Note that i and j are not the same in the question, the correct answer here is:
x = log(1:n) * sum(exp((1:m).^2))
as discussed in the comments above.

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