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translating commands from python

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HC98
HC98 2020-1-31
编辑： Stephen23 2020-1-31
So I'm trying to translate the following code from Python:
def chabrier03individual(m):
k = 0.158 * exp(-(-log(0.08))**2/(2 * 0.69**2))
return numpy.where(m <= 1,\
0.158*(1./m) * exp(-(log(m)-log(0.08))**2/(2 * 0.69**2)),\
k*m**-2.3)
And end up stuck with an incorrect if statement:
% 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
Where am I going wrong?
  2 个评论
Geoff Hayes
Geoff Hayes 2020-1-31
HC98 - m appears to be an array with 400 elements, so what are you expecting to happen with
if m<=1
Is this logic that you want to apply to each element of m? Also, why is u used if m<=1 but v used for the else?
HC98
HC98 2020-1-31
the expectation is that this function is applied to values of m less than 1.

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回答（1 个）

Stephen23
Stephen23 2020-1-31
编辑：Stephen23 2020-1-31
The equivalent to numpy's where is to use indexing:
https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html
x = ...;
y = ...;
idx = m<=1;
z = y;
z(idx) = x(idx)
Using if is a red herring (it would require a loop, which is a waste of MATLAB).

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