Why does my <= statement not work?
显示 更早的评论
I'm running a simple loop that applies a less than or equal to inequality to a value. Unfortunately, it is overlooking this value and not working. Here is my code
% Initial Conditions
clearvars
close all
Ms=1.989E30;
m = logspace(-2, 2, 400);
% m = 1E2:100:1E4
% (m<0.08, m**-0.3, numpy.where(m < 0.5, 0.08**-0.3 * (m/0.08)**-1.3, 0.08**-0.3 * (0.5/0.08)**-1.3 * (m/0.5)**-2.3))
%% def chabrier03individual(m):
k = 0.158*exp(-(-log(0.08))^2/(2*0.69^2))
if m<=1
u = 0.158*(1./m)*exp(-(log(m)-log(0.08))^2/(2 * 0.69^2));
else
v = k*m;
end
1 个评论
The comprison works as documented. Note the if documentation states " An expression is true when its result is nonempty and contains only nonzero elements (logical or real numeric). Otherwise, the expression is false."
You provided if with a 1x400 logical vector as its condition, it contains no non-zero elements:
>> nnz(m<=1)
ans = 0
Based on this I would expect the else part to be executed, and this is indeed what occurs when i run your code.
Note that your vector m contains just one value repeated 400 times over:
>> unique(m)
ans = 100
It is not clear why you wanted to create that 1x400 vector in such an obfuscated way.
EDIT: the OP originally defined
m = logspace(2, 2, 400);
but has since edited the question and changed it to:
m = logspace(-2, 2, 400);
The relevance of reading the if documentation is unchanged.
回答（1 个）
Shekhar Vats
2020-1-31
0 个投票
Can you please say more about your issue ? It's working as expected for me.
7 个评论
HC98
2020-1-31
Stephen23
2020-1-31
"I couldn't get the u value to print,"
Because your if condition is not true, I see no reason to expect u to be defined.
Stephen23
2020-1-31
HC98' "Answer" moved here:
Apologies, I made an error in my code, I've added the correct version here
HC98
2020-1-31
"U shoiuld be defined."
No. Your non-scalar logical vector does not contain only non-zeros:
>> nnz(m<=1)
ans = 200
>> numel(m)
ans = 400
Read the if documenttion to understand why this is relevant.
Most likely using if is entirely the wrong approach anyway, and you should be using indexing.
HC98
2020-1-31
x = ...;
y = ...;
idx = m<=1;
z = y;
z(idx) = x(idx)
类别
在 帮助中心 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
