MATLAB和系列函数

Question

我是Matlab的新手。我只是尝试实现系列1 + x + x ^ 2/2！+ x ^ 3/3的总和！.....但我无法找到如何做到这一点。到目前为止，我只做了一些数字。请帮忙。

for ii = 1:length(a)
    sum_a = sum_a + a(ii)
    sum_a



end

Answer 1

n = 0 : 10; % elements of the series
x = 2;  % value of x
s = sum(x .^ n ./ factorial(n)); % sum

Answer 2

你的答案的第二部分是：

n = 0:input('variable?')

Answer 3

当系列的术语数量很少时，

Cheery's approach完全有效。对于较大的值，更快的方法如下。这样更有效，因为它避免了重复乘法：

m = 10;
x = 2;
result = 1+sum(cumprod(x./[1:m]));

m = 1000; x = 1;

的运行时间示例

tic
for k = 1:1e4
    result = 1+sum(cumprod(x./[1:m]));
end 
toc

tic
for k = 1:1e4
    result = sum(x.^(0:m)./factorial(0:m));
end 
toc

给出

Elapsed time is 1.572464 seconds.
Elapsed time is 2.999566 seconds.