Sum digits after vpa(N,100) ?

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Per on 16 Jan 2013
Hi MatLab!
I've stumbled across a problem. I wish to take all the first hundred digits in the square root of 2 ---> sqrt(2) and sum them up.
I first use
N=sym('sqrt(2)'); vpa(N,100)
which gives me alot of digits. But when I try to num2str the answer it cant be done. How can I achieve this?

Accepted Answer

Shashank Prasanna
Shashank Prasanna on 16 Jan 2013
Here you go:
clear all
sumA = 0;
for i = 1:100
sumA = sumA + (floor(N*(10^(i-1))) - 10*floor(N*10^(i-2)));

More Answers (1)

Jan on 16 Jan 2013
Edited: Jan on 16 Jan 2013
Could you operate on the VPA number instead of converting it to a string? I do not have the Symbolic Toolbox, but I guess:
s = 0;
x = vpa(N, 100);
for ii = 1:100
s = s + floor(x);
x = rem(x, 1) * 10;
Does this work?
N = sym('sqrt(2)');
x = vpa(N, 100);
s = 0;
for ii = 1:100
f = floor(x);
s = s + f;
x = (x - f) * 10;
If rounding error appear, try it with 200 digits in the VPA command. Please use this as inspiration - as I said already, I do not have the corresponding toolboxes.
Jan on 16 Jan 2013
Now I can run Matlab again. The [EDITED] version works and gives the correct result.

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