244-2: MATLAB/PYTHON FUNDAMENTALS Scalars To assign a single value to a variable, simply type the variable name, the = sign, and the value: >> a = 4 a= 4 Note that variable names must start with a letter, though they can contain letters, numbers, and the underscore (_) symbol Array Creation % Matlab command to create a vector >>x = [ 1 2 3 4 5]
ans = 12345 # Python command to create a vector Import numpy as np x = np.array([1,2,3,4,5]) x Matrix creation % Matlab command x=[1 2 3; 4 5 6; 7 8 9]; ans = 123 456 789
# Python command import numpy as np x=np.array([[1,2,3], [4,5,6], [7,8,9]]) x Mathematical Operations Mathematical operations in MATLAB/Python can be performed on both scalars and arrays Matlab 4^2 = 16 2*8 = 16 32/4 = 8 Python
4**2 =16 2*8 = 16 32/4 = 8 Generate p pi Import numpy as np 2*np.pi = 6.2832 np.pi/4 = 0.7854 Addition and Subtraction
3+5 = 8 3-5 = -2 3+5 = 8 3-5 = -2 Exponent Multiplication and Division Complex Numbers in Matlab/Python All operations can be used with complex quantities
x*y x/y x+y x-y Values containing an imaginary part are entered using: x = 2+4j Matrix Calculations in Matlab/Python MATLAB/Python can also perform operations on vectors and matrices. For example, multiply the two matrices: A= 367 5 -3 0 B=1 1
2 1 3 -3 Matlab A = [ 3 6 7; 5 -3 0] B = [1 1; 2 1; 3 -3] C = A*B Python import numpy as np A = np.array([[3, 6, 7], [5, -3, 0]]) B = np.array([[1, 1], [2, 1], [3, -3]]) C = A.dot(B) print(C)
Element-by-Element Calculations At times, you will want to carry out calculations item by item in a matrix or vector. They are also often referred to as element-by-element operations. For array operations, both matrices must be the same size A= 367 B=1 11 5 -3 0 2 13 Matlab A = [ 3 6 7; 5 -3 0] B = [1 1 1; 2 1 3] C = A.*B
Python import numpy as np A = np.array([[3, 6, 7], [5, -3, 0]]) B = np.array([[1, 1, 1], [2, 1, 3 ]) C = A*B print(C) Graphics in Matlab/Python MATLAB/Python have a common plot command to graph vectors Matlab x = [ 3 6 7] y = [1 2 3]
plot(x,y) Python import numpy as np import matplotlib.pyplot as plt x = np.array([3,6,7]) y = np.array([1,2,3]) plt.plot(x,y) Other Matlab Plotting Commands hold on and hold off hold on will keep the current plot active Enables the user to superimpose plots on each other
hold off will release the current plot subplot(m, n, p) subplot command enables multiple plots on a single page Divides the page into m x n sections Conditional IF Loops For Loops % Matlab x=0 for i = 1:10; x=x+I end
# Python x=0 for i in range(1,10): sum = sum + x print(sum) Example of Input command Let us say you want to enter todays date clear month = input(enter month,1-12 ) day = input(enter day, 1-31 ) year = input(enter year,20xx ) today_date=[month day year]
Relational Operators Summary of relational operators in MATLAB/Python Example x == 0 unit ~= m a < 0 s > t 3.9 <= a/3 r >= 0 Operator == ~=
< > <= >= Relationship Equal Not equal Less than Greater than Less than or equal to Greater than or equal to