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Commit 74aedbbe authored by Jennifer Rinker's avatar Jennifer Rinker
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moving md so it doesnt clutter repo

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# This is a work in progress
Please don't read this. It requires a lot of formatting.
For now, you can read all of this in a PDF [here](https://gitlab.windenergy.dtu.dk/python-at-risoe/scientific-python-workshops/2-getting-started/blob/master/matlab_vs_python.pdf).
# Placing text below so I don't lose it, but it is not useful to others now
Originally from [this page](http://reactorlab.net/resources-folder/matlab/P_to_M.html)
but modified to 1) be in markdown, 2) fix some errors, and 3) add more detail.
<table>
<tr>
<th>Python</th>
<th>Matlab</th>
</tr>
<tr>
<td><ul>
<li>numeric variables are double precision if decimal added</li>
</ul>
<pre><code>a = 5. # this is a float
a = 5 # this is an int</code></pre>
</td>
<td><ul>
<li>numeric variables are double precision by default</li>
</ul>
<pre><code>a = 5.0; % this is a double</code></pre>
</td>
</tr>
<tr>
<td>Eve</td>
<td>Jackson</td>
</tr>
</table>
# test
numeric arrays are objects defined in NumPy package <br /> indexes start at 0 in Python <br /> structures are defined by indentation, no 'end' <br /> `A = np.empty(10) # initialize array A`| array indexes start at 1 in Matlab <br /> indentation is for readability only <br /> `for i=1:10` <br /> ` A(i) = i;`
for i in range(1,11): | end
A.append(i) | A % display contents of A
print(A[i-1]) |
|
# repeat which prints a series of |
# values | for i=0:2:10
| fprintf(' %i \n', i)
for i in range(0,11,2): | end
print(i) |
|
# initialize an identity matrix |
| % MATLAB has built-in functions for
# import the numpy library for matrix operations | % common array initializations
|
import numpy as np | B = eye(100);
|
B = np.identity(3) |
|
# declare and initialize an array, | C = [1, 2, 3]; % or C = [1 2 3];
# known as a list in Python |
|
C = [1, 2, 3] |
|
# initialize and print an array |
# array name = arange(start,stop,step) | % array name = [start:increment:end];
|
import numpy as np |
C = np.arange(2,10,2) | C = [2:2:8] % leave off ; to display value
print(C) |
|
# print an array element on screen |
# array indexes start at 0 | % array indexes start at 1
|
print(C[1]) | C(2)
|
# prints 4 using C from above table cell | % prints 4 using C from above table cell
# note square brackets C[1] | % note parentheses C(2)
|
# declare and initialize an array |
# with fixed interval between values |
import numpy as np |
C = np.linspace(2,8,4) | C = linspace(2,8,4);
# third param is optional and = # points |
# between and including 1st two points | % third param is optional and = # points
# if third param left off, default | % between and including 1st two points
# is 50 points | % if third param left off, default
| % is 100 points
# initialize a 2D array | % these three examples accomplish the
| % same thing
|
D = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] | D = [1 2 3; 4 5 6; 7 8 9];
| D = [1:3; 4:6; 7:9];
| D = [1 2 3
| 4 5 6
| 7 8 9];
# print element of 2D array | % array indexes start at 1
# array indexes start at 0 |
print(D[1][1]) # row 2, column 2 |
# prints 5 using D from above table cell | D(2,2) % row 2, column 2
| % prints 5 using D from above table cell
# print selected sub array of 2D array |
# e.g., print rows 1 to 2 of column 1 |
| D(1:2,1) % rows 1 to 2 of column 1
for i in range(0,2): |
print(D[i][0]) |
|
# print all rows of column 1 of 2D |
# array |
|
import numpy as np | D(:,1) % all rows, column 1
D = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) |
Dsub = D[0:,0:1] |
print(Dsub) |
|
# logical expression |
|
a = 1 | a = 1
b = 2 | b = 2;
if a == 1 or b == 3: | if a == 1 || b == 3
print('a = 2 or b = 3') | fprintf('a = 2 or b = 3 \n');
| end
|
# if structure |
|
if a == 1 and b != 3: | if a == 1 && b ~= 3
print('a=1 and b not 3'); | fprintf('a=1 and b not 3 \n');
print('OK?') | fprintf('OK? \n');
| end
|
# if, else structure |
| a ~= 1
if a != 1: | fprintf('a is not 1 \n')
print('a is not 1') | elseif b ~= 3
elif b != 3: | fprintf('b is not 3 \n')
print('b is not 3') | else
else: | fprintf('huh? \n')
print('huh?') | end
|
# switch structure |
| switch menuChoice
# Python doesn't have a switch structure | case 1
| % can do any actions in a case, e.g.,
# any switch structure can be | % call a user-defined function
# written as an if-else structure | myMenuFunc01();
| case 2
# switch structures may be quicker to | myMenuFunc02();
# read and write for applications such as menus | case 3
| myMenuFunc03();
| otherwise
| fprintf('invalid selection, try again')
| end
|
# program which calls a user-defined function | % main program and function definition must
| % be in separate files and function file
# define function, here I chose name myfunc | % must have same name as function name
|
def myfunc(x,y): | z = myfunc(2,3)
return x**y # ** is exponentiation operator | % prints 8 for this input
|
# call function | ----- LISTING OF FILE myfunc.m ------
|
z = myfunc(2,3) | function returnValue = myfunc(x,y)
print(z) | returnValue = x^y; % ^ is exponentiation operator
# prints 8 for this input |
| % function is a keyword
| % returnValue is arbitrary variable name
|
# matrix multiplication |
|
import numpy as np |
| A = [2,3; 3,5];
A = np.matrix( ((2,3), (3, 5)) ) | B = [1,2; 5,-1];
B = np.matrix( ((1,2), (5, -1)) ) |
| C = A * B
C = A * B |
print(C) |
|
# plotting |
|
import numpy as np |
import matplotlib.pyplot as plt |
x = np.linspace(0,2*np.pi,100) | x = linspace(0,2*pi,100);
y = np.sin(x) | y = sin(x);
plt.plot(x,y) | plot(x,y)
plt.ylabel('sin(x)') | ylabel('sin(x)')
plt.xlabel('x') | xlabel('x')
plt.show() |
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