I am working on matlab conversion code to python.
I do not understand these 2 lines of code.
d1 = s(1:3,2) - s(1:3,1);
d2 = s(1:3,end) - s(1:3,end-1);
what these 2 lines are doing? can anyone explain me?
and how will i convert this in python?
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sam
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Have tried printing the results by parts in MATLAB? What did you get? – Christian Tapia Jan 06 '14 at 05:40
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i do not have matlab but I need to do conversion – sam Jan 06 '14 at 05:41
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2Try [this](http://www.compileonline.com/execute_matlab_online.php) to run MATLAB code online. – Christian Tapia Jan 06 '14 at 05:42
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thanks. can you tell me any documentation which will direct me towards easy conversion of matlab code to python code? – sam Jan 06 '14 at 06:04
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1Try [this answer](http://stackoverflow.com/a/17535694/2670792) in another SO post. – Christian Tapia Jan 06 '14 at 06:06
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2Also have a look at this: http://wiki.scipy.org/NumPy_for_Matlab_Users – Dan Jan 06 '14 at 06:22
3 Answers
3
In Matlab:
% Matlab
s = [1,2,3,4,5; ...
6,7,8,9,10; ...
11,12,13,14,15];
d1 = s(1:3,2) - s(1:3,1);
d2 = s(1:3,end) - s(1:3,end-1);
disp('--s--')
disp(s)
disp('--d1--')
disp(d1)
disp('--d2--')
disp(d2)
disp('--s(1:3,2)--')
disp(s(1:3,2))
disp('--s(1:3,1)--')
disp(s(1:3,1))
disp('--s(1:3,end)--')
disp(s(1:3,end))
disp('--s(1:3,end-1)--')
disp(s(1:3,end-1))
can be translated to Python as:
# Python
import numpy as np
s = np.asarray([ \
1,2,3,4,5, \
6,7,8,9,10, \
11,12,13,14,15]).reshape(3,-1);
d1 = s[0:3,1] - s[0:3,0];
d2 = s[0:3,-1] - s[:3,-2];
print '--s--'
print s
print '--d1--'
print d1
print '--d2--'
print d2
print '--s[0:3,1]--'
print s[0:3,1]
print '--s[0:3,0]--'
print s[0:3,0]
print '--s[0:3,-1]--'
print s[0:3,-1]
print '--s[0:3,-2]--'
print s[0:3,-2]
Results of Matlab:
--s--
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
--d1--
1
1
1
--d2--
1
1
1
--s(1:3,2)--
2
7
12
--s(1:3,1)--
1
6
11
--s(1:3,end)--
5
10
15
--s(1:3,end-1)--
4
9
14
vs of Python:
--s--
[[ 1 2 3 4 5]
[ 6 7 8 9 10]
[11 12 13 14 15]]
--d1--
[1 1 1]
--d2--
[1 1 1]
--s[0:3,1]--
[ 2 7 12]
--s[0:3,0]--
[ 1 6 11]
--s[0:3,-1]--
[ 5 10 15]
--s[0:3,-2]--
[ 4 9 14]
They match.
Evaluate Matlab code online /here/ and Python code /here/, /here/ and with packages /here/.
Developer
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I'd probably prefer `np.array([[1,2,3,4,5], [6,7,8,9,10], [11,12,13,14,15]])` there - note that you don't need `\ ` to continue a line within `{[(` – Eric Jan 06 '14 at 11:43
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@Eric Your point is totally correct. We just tried to keep `Python` translation similar to `Matlab` code as much as possible. – Developer Jan 06 '14 at 12:09
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2
s is a matrix. s(1:3,2) creates a vector from rows 1 to 3 and column 2. s(1:3,1) creates a vector from rows 1 to 3 and column 1. d1 is then another vector being the element by element difference
end is special syntax for the last row or column. end-1 is the penultimate row/column
David Waterworth
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