From d1bf07bac3e64e3e4cbe3581b03343c147d13356 Mon Sep 17 00:00:00 2001
From: rink <rink@dtu.dk>
Date: Thu, 28 Sep 2017 11:16:12 +0200
Subject: [PATCH] Initial upload of py vs mat
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+# Comparison of Python and Matlab
+
+Originally from [this page](http://reactorlab.net/resources-folder/matlab/P_to_M.html)
+but modified to fix some errors and add more detail.
+
+Python | Matlab
+# numeric variables | %Â numeric variables
+# are double precision by default | % are double precision by default
+ |
+a = 5.0 | a = 5.0;
+ |
+# repeat which assigns values to array elements |
+# arrays are known as "lists" in Python | % array indexes start at 1 in Matlab
+# array indexes start at 0 in Python | % indentation is for readability only
+# structures are defined by indentation, no 'end' |
+ | for i=1:10
+A = [] # initialize array A | Â Â Â Â A(i) =Â i;
+for i in range(1,11): | end
+Â Â Â A.append(i) | A % display contents of A
+Â Â Â print(A[i-1])Â |
+ |
+# repeat which prints a series of |
+# values | for i=0:2:10
+ |     fprintf(' %i \n', i)
+for i in range(0,11,2): | end
+Â Â Â 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]Â % leave off ; to display value
+print(C) |
+ |
+# print an array element on screen |
+# array indexes start at 0Â Â | % array indexes start at 1
+ |
+print(C[1])Â | 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 =Â 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
+ | Â Â Â Â Â 4 5 6
+ | Â Â Â Â Â 7 8 9];
+# print element of 2D array | % array indexes start at 1
+# array indexes start at 0Â | Â Â
+print(D[1][1]) # row 2, column 2 |
+#Â prints 5Â using D from above table cell | D(2,2) % row 2, column 2
+ | % prints 5Â using D from above table cell
+# print selected sub array of 2D array |
+#Â e.g., print rows 1 to 2 of column 1Â |
+ | D(1:2,1) % rows 1 to 2 of column 1
+for i in range(0,2): |
+Â Â Â 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
+Â Â Â print('a = 2 or b = 3') | Â Â Â Â fprintf('a = 2 or b = 3 \n');
+ | endÂ
+ |
+#Â if structure |
+ |
+if a == 1 and b != 3: | if a == 1 && b ~= 3
+Â Â Â print('a=1 and b not 3'); | Â Â Â Â fprintf('a=1 and b not 3 \n');
+   print('OK?') |     fprintf('OK? \n');
+ | end
+ |
+# if, else structure |
+ | a ~= 1
+if a != 1: | Â Â Â Â fprintf('a is not 1 \n')
+Â Â Â print('a is not 1') | elseif b ~= 3Â
+elif b != 3: | Â Â Â Â fprintf('b is not 3 \n')
+Â Â Â print('b is not 3') | else
+else: | Â Â Â Â fprintf('huh? \n')
+Â Â Â print('huh?') | end
+ |
+# switch structure |
+ | switch menuChoice
+# Python doesn't have a switch structure | Â Â Â Â case 1
+ | Â Â Â Â Â Â Â % can do any actions in a case, e.g.,
+# any switch structure can be | Â Â Â Â Â Â Â % call a user-defined function
+# written as an if-else structure | Â Â Â Â Â Â Â Â myMenuFunc01();
+ | Â Â Â Â case 2
+# switch structures may be quicker to |         myMenuFunc02();
+# read and write for applications such as menus | Â Â Â Â case 3
+ | Â Â Â Â Â Â Â Â myMenuFunc03();
+ | Â Â Â Â otherwise
+ | Â Â Â Â Â Â Â Â 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 =Â myfunc(2,3)
+Â Â Â return x**y # ** is exponentiation operator | % prints 8 for this input
+ |
+# call function | ----- LISTING OF FILEÂ myfunc.m ------
+ |
+z = myfunc(2,3) | function returnValue = myfunc(x,y)
+print(z) | Â Â returnValue = x^y; % ^ is exponentiation operator
+# prints 8 for this input |
+ | Â Â % function is a keyword
+ | Â Â % returnValue is arbitrary variable name
+ | Â Â Â Â Â
+# matrix multiplication | Â Â
+ | Â Â
+import numpy as np | Â Â
+ | AÂ = [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)Â |
+ |
+# 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')Â
+plt.show()Â |
+
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