Matlab and Numpy/Python functions side by side

Vidar Bronken Gundersen, @ mathesaurus.sf.net originally created an excellent Matlab-Python side-by-side comparison table which I think is very useful for some moving from Matlab to Python. However, it seems that the page was last updated in 2007, and a whole lot has changed since then. So, I have decided to update his table here. Please note that I have duly attributed the source of this table to him. Also, here is a copy of the copyright text from his website.

©2006 Vidar Bronken Gundersen, /mathesaurus.sf.net
Permission is granted to copy, distribute and/or modify this document as long as the above attribution is retained.

In addition to the mathesaurus.sf.net website, one should also refer to “NumPy for Matlab Users” at Scipy.org which too has very highly valubable information for anyone migrating from Matlab to Python/Numpy.

It is assumed that the required modules in Python has been imported in the following way:

import numpy as np
import scipy as sp
import scipy.linalg as spl
import matplotlib.pyplot as plt

Help

MATLAB/Octave	Python	Description
`dochelp -i % browse with Info`	`help()`	Browse help interactively
`help help` or `doc doc`	`help`	Help on using help
`help plot`	`help(plot)` or `?plot`	Help for a function
`help splines` or `doc splines`	`help(pylab)`	Help for a toolbox/library package
`demo`		Demonstration examples

Searching available documentation

MATLAB/Octave	Python	Description
`lookfor plot`	`np.lookfor('plot')`	Search help files
`help`	`help(); modules [Numeric]`	List available packages
`which plot`	`help(plot)`	Locate functions

Using interactively

MATLAB/Octave	Python	Description
`octave -q`	`ipython -pylab`	Start session
`TAB` or `M-?`	`TAB`	Auto completion
`foo(.m)`	`execfile('foo.py')` or `run foo.py`	Run code from file
`history`	`hist -n`	Command history
`diary on [..] diary off`		Save command history
`exit` or `quit`	`CTRL-D` `CTRL-Z # windows` `sys.exit()`	End session

Operators

MATLAB/Octave	Python	Description
`help -`		Help on operator syntax

Arithmetic operators

MATLAB/Octave	Python	Description
`a=1; b=2;`	`a=1; b=1`	Assignment; defining a number
`a + b`	`a + b` or `add(a,b)`	Addition
`a - b`	`a - b` or `subtract(a,b)`	Subtraction
`a * b`	`a * b` or `multiply(a,b)`	Multiplication
`a / b`	`a / b` or `divide(a,b)`	Division
`a .^ b`	`a ** b` `power(a,b)` `pow(a,b)`	Power, $a^b$
`rem(a,b)`	`a % b` `remainder(a,b)` `fmod(a,b)`	Remainder
`a+=1`	`a+=b` or `add(a,b,a)`	In place operation to save array creation overhead
`factorial(a)`		Factorial, $n!$

Relational operators

MATLAB/Octave	Python	Description
`a == b`	`a == b` or `equal(a,b)`	Equal
`a < b`	`a < b` or `less(a,b)`	Less than
`a > b`	`a > b` or `greater(a,b)`	Greater than
`a <= b`	`a <= b` or `less_equal(a,b)`	Less than or equal
`a >= b`	`a >= b` or `greater_equal(a,b)`	Greater than or equal
`a ~= b`	`a != b` or `not_equal(a,b)`	Not Equal

Logical operators

MATLAB/Octave	Python	Description
`a && b`	`a and b`	Short-circuit logical AND
`a \|\| b`	`a or b`	Short-circuit logical OR
`a & b` or `and(a,b)`	`logical_and(a,b)` or `a and b`	Element-wise logical AND
`a \| b` or `or(a,b)`	`logical_or(a,b)` or `a or b`	Element-wise logical OR
`xor(a, b)`	`logical_xor(a,b)`	Logical EXCLUSIVE OR
`~a` or `not(a)` `~a` or `!a`	`logical_not(a)` or `not a`	Logical NOT
`any(a)`		True if any element is nonzero
`all(a)`		True if all elements are nonzero

Root and logarithm

MATLAB/Octave	Python	Description
`sqrt(a)`	`math.sqrt(a)`	Square root
`log(a)`	`math.log(a)`	Logarithm, base $e$ (natural)
`log10(a)`	`math.log10(a)`	Logarithm, base 10
`log2(a)`	`math.log(a, 2)`	Logarithm, base 2 (binary)
`exp(a)`	`math.exp(a)`	Exponential function

Round off

MATLAB/Octave	Python	Description
`round(a)`	`around(a)` or `math.round(a)`	Round
`ceil(a)`	`ceil(a)`	Round up
`floor(a)`	`floor(a)`	Round down
`fix(a)`	`fix(a)`	Round towards zero

Mathematical constants

MATLAB/Octave	Python	Description
`pi`	`math.pi`	$\pi=3.141592$
`exp(1)`	`math.e` or `math.exp(1)`	$e=2.718281$

Missing values; IEEE-754 floating point status flags

MATLAB/Octave	Python	Description
`NaN`	`nan`	Not a Number
`Inf`	`inf`	Infinity, $\infty$
	`plus_inf`	Infinity, $+\infty$
	`minus_inf`	Infinity, $-\infty$
	`plus_zero`	Plus zero, $+0$
	`minus_zero`	Minus zero, $-0$

Complex numbers

MATLAB/Octave	Python	Description
`i`	`z = 1j`	Imaginary unit
`z = 3+4i`	`z = 3+4j` or `z = complex(3,4)`	A complex number, $3+4i$
`abs(z)`	`abs(3+4j)`	Absolute value (modulus)
`real(z)`	`z.real`	Real part
`imag(z)`	`z.imag`	Imaginary part
`arg(z)`		Argument
`conj(z)`	`z.conj(); z.conjugate()`	Complex conjugate

Trigonometry

MATLAB/Octave	Python	Description
`atan(y/x)`	`atan(y/x)`	Inverse tangent, $\arctan(y/x)$ . The range is in $[-\pi/2, \pi/2]$
`atan2(y,x)`	`atan2(y,x)`	Four-quadrant inverse tangent, $\arctan(y/x)$ . It considers the signs of $x$ and $y$ to determine the specific quadrant. The range is in $[-\pi, \pi]$
	`hypot(x,y)`	Hypotenus; Euclidean distance

Generate random numbers

MATLAB/Octave	Python	Description
`rand(1,10)`	`random.random((10,))` `random.uniform((10,))`	Uniform distribution
`2+5*rand(1,10)`	`random.uniform(2,7,(10,))`	Uniform: Numbers between 2 and 7
`rand(6)`	`random.uniform(0,1,(6,6))`	Uniform: 6,6 array
`randn(1,10)`	`random.standard_normal((10,))`	Normal distribution

Vectors

MATLAB/Octave	Python	Description
`a=[2 3 4 5];`	`a=array([2,3,4,5])`	Row vector, $1 \times n$ -matrix
`adash=[2 3 4 5]';`	`array([2,3,4,5])[:,NewAxis]` `array([2,3,4,5]).reshape(-1,1)` `r_[1:10,'c']`	Column vector, $m \times 1$ -matrix

Sequences

MATLAB/Octave	Python	Description
`1:10`	`arange(1,11, dtype=Float)` `range(1,11)`	1,2,3, … ,10
`0:9`	`arange(10.)`	0.0,1.0,2.0, … ,9.0
`1:3:10`	`arange(1,11,3)`	1,4,7,10
`10:-1:1`	`arange(10,0,-1)`	10,9,8, … ,1
`10:-3:1`	`arange(10,0,-3)`	10,7,4,1
`linspace(1,10,7)`	`linspace(1,10,7)`	Linearly spaced vector of n=7 points
`reverse(a)`	`a[::-1]` or	Reverse
`a(:) = 3`	`a.fill(3), a[:] = 3`	Set all values to same scalar value

Concatenation (vectors)

MATLAB/Octave	PYTHON	Description
`[a a]`	`concatenate((a,a))`	Concatenate two vectors
`[1:4 a]`	`concatenate((range(1,5),a), axis=1)`

Repeating elements of an array

MATLAB/Octave	Python	Description
`kron(a,ones(1,3))`	`a.repeat(3)` or `kron(a,ones(3))`	`[1, 1, 1, 2, 2, 2, 3, 3, 3,]` where, `a=[1,2,3]`
`kron(a,ones(3,1))`	`kron(a,ones((3,1)))` or `repeat(matrix(a),3,0)` or `tile(a,(3,1))`	`[[ 1, 2, 3], [ 1, 2, 3], [ 1, 2, 3]]` Note that the second Python option (`repeat(...)`) outputs a matrix and it works because each row is considered as an element of the array which gets repeated.
	`a.repeat(a)` or `np.repeat(a,a)`	`[1, 2, 2, 3, 3, 3]`
	`x.repeat(2)` or `np.repeat(x,2)`	`[0, 0, 1, 1, 2, 2, 3, 3]` where `x =[[0, 1], [2, 3]]`
	`x.repeat(2,0)` or `np.repeat(x,2,0)`	`[[0, 1], [0, 1], [2, 3], [2, 3]]`
	`x.repeat(2,1)` or `np.repeat(x,2,1)`	`[[0, 0, 1, 1], [2, 2, 3, 3]]`

Miss those elements out

MATLAB/Octave	Python	Description
`a(2:end)`	`a[1:]`	miss the first element
`a([1:9])`		miss the tenth element
`a(end)`	`a[-1]`	last element
`a(end-1:end)`	`a[-2:]`	last two elements

Maximum and minimum

MATLAB/Octave	Python	Description
`max(a,b)`	`maximum(a,b)`	pairwise max
`max([a b])`	`concatenate((a,b)).max()`	max of all values in two vectors
`[v,i] = max(a)`	`v,i = a.max(0),a.argmax(0)`

Vector multiplication

MATLAB/Octave	Python	Description
`a.*a`	`a*a`	Multiply two vectors
`dot(u,v)`	`dot(u,v)`	Vector dot product, $u \cdot v$

Matrices

MATLAB/Octave	Python	Description
`a = [2 3;4 5]`	`a = array([[2,3],[4,5]])`	Define a matrix

Concatenation (matrices); rbind and cbind

MATLAB/Octave	Python	Description
`[a ; b]`	`concatenate((a,b), axis=0)` `vstack((a,b))`	Bind rows
`[a , b]`	`concatenate((a,b), axis=1)` `hstack((a,b))`	Bind columns
	`concatenate((a,b), axis=2)` `dstack((a,b))`	Bind slices (three-way arrays)
`[a(:), b(:)]`	`concatenate((a,b), axis=None)`	Concatenate matrices into one vector
`[1:4 ; 1:4]`	`concatenate((r_[1:5],r_[1:5])).reshape(2,-1)` `vstack((r_[1:5],r_[1:5]))`	Bind rows (from vectors)
`[1:4 ; 1:4]'`		Bind columns (from vectors)

Array creation

MATLAB/Octave	Python	Description
`zeros(3,5)`	`zeros((3,5),Float)`	0 filled array
	`zeros((3,5))`	0 filled array of integers
`ones(3,5)`	`ones((3,5),Float)`	1 filled array
`ones(3,5)*9`		Any number filled array
`eye(3)`	`identity(3)`	Identity matrix
`diag([4 5 6])`	`diag((4,5,6))`	Diagonal
`magic(3)`		Magic squares; Lo Shu
	`a = empty((3,3))`	Empty array

Reshape and flatten matrices

MATLAB/Octave	Python	Description
`reshape(1:6,3,2)';`	`arange(1,7).reshape(2,-1)` `a.setshape(2,3)`	Reshaping (rows first)
`reshape(1:6,2,3);`	`arange(1,7).reshape(-1,2).transpose()`	Reshaping (columns first)
`a'(:)`	`a.flatten()` or	Flatten to vector (by rows, like comics)
`a(:)`	`a.flatten(1)`	Flatten to vector (by columns)
`vech(a)`		Flatten upper triangle (by columns)

Shared data (slicing)

MATLAB/Octave	Python	Description
`b = a`	`b = a.copy()`	Copy of a

Indexing and accessing elements (Python: slicing)

MATLAB/Octave	Python	Description
`a = [ 11 12 13 14 ...` `21 22 23 24 ...` `31 32 33 34 ]`	`a = array([[ 11, 12, 13, 14 ],` `[ 21, 22, 23, 24 ],` `[ 31, 32, 33, 34 ]])`	Input is a 3,4 array
`a(2,3)`	`a[1,2]`	Element 2,3 (row,col)
`a(1,:)`	`a[0,]`	First row
`a(:,1)`	`a[:,0]`	First column
`a([1 3],[1 4]);`	`a.take([0,2]).take([0,3], axis=1)`	Array as indices
`a(2:end,:)`	`a[1:,]`	All, except first row
`a(end-1:end,:)`	`a[-2:,]`	Last two rows
`a(1:2:end,:)`	`a[::2,:]`	Strides: Every other row
	`a[...,2]`	Third in last dimension (axis)
`a(:,[1 3 4])`	`a.take([0,2,3],axis=1)`	Remove one column
	`a.diagonal(offset=0)`	Diagonal

Assignment

MATLAB/Octave	Python	Description
`a(:,1) = 99`	`a[:,0] = 99`
`a(:,1) = [99 98 97]'`	`a[:,0] = array([99,98,97])`
`a(a>90) = 90;`	`(a>90).choose(a,90)` `a.clip(min=None, max=90)`	Clipping: Replace all elements over 90
	`a.clip(min=2, max=5)`	Clip upper and lower values

Linear Algebra, transpose and inverse

MATLAB/Octave	Python	Description
`a'`	`a.conj().transpose()`	Transpose
`a.'` or `transpose(a)`	`a.transpose()`	Non-conjugate transpose
`det(a)`	`linalg.det(a)` or	Determinant
`inv(a)`	`linalg.inv(a)` or	Inverse
`pinv(a)`	`linalg.pinv(a)`	Pseudo-inverse
`norm(a)`	`norm(a)`	Norms
`eig(a)`	`linalg.eig(a)[0]`	Eigenvalues
`svd(a)`	`linalg.svd(a)`	Singular values
`chol(a)`	`linalg.cholesky(a)`	Cholesky factorization
`[L,U,P]=lu(a)`	`P,L,U = spl.linalg.lu(a)`	LU factorization. Note that P(matlab) == Transpose(P(scipy))
`[v,l] = eig(a)`	`linalg.eig(a)[1]`	Eigenvectors
`rank(a)`	`np.rank(a)`	Rank

Sum

MATLAB/Octave	Python	Description
`sum(a)`	`a.sum(axis=0)`	Sum of each column
`sum(a')`	`a.sum(axis=1)`	Sum of each row
`sum(sum(a))`	`a.sum()`	Sum of all elements
	`a.trace(offset=0)`	Sum along diagonal
`cumsum(a)`	`a.cumsum(axis=0)`	Cumulative sum (columns)

Sorting

MATLAB/Octave	Python	Description
`a = [ 4 3 2 ; 2 8 6 ; 1 4 7 ]`	`a = array([[4,3,2],[2,8,6],[1,4,7]])`	Example data
`sort(a(:))`	`a.ravel().sort()` or	Flat and sorted
`sort(a)`	`a.sort(axis=0)` or `msort(a)`	Sort each column
`sort(a')'`	`a.sort(axis=1)`	Sort each row
`sortrows(a,1)`	`a[a[:,0].argsort(),]`	Sort rows (by first row)
	`a.ravel().argsort()`	Sort, return indices
	`a.argsort(axis=0)`	Sort each column, return indices
	`a.argsort(axis=1)`	Sort each row, return indices

Maximum and minimum

MATLAB/Octave	Python	Description
`max(a)`	`a.max(0)` or `amax(a [,axis=0])`	max in each column
`max(a')`	`a.max(1)` or `amax(a, axis=1)`	max in each row
`max(max(a))`	`a.max()` or	max in array
`[v i] = max(a)`		return indices, i
`max(b,c)`	`maximum(b,c)`	pairwise max
`cummax(a)`
	`a.ptp(); a.ptp(0)`	max-to-min range

Matrix manipulation

MATLAB/Octave	Python	Description
`fliplr(a)`	`fliplr(a)` or `a[:,::-1]`	Flip left-right
`flipud(a)`	`flipud(a)` or `a[::-1,]`	Flip up-down
`rot90(a)`	`rot90(a)`	Rotate 90 degrees
`repmat(a,2,3)` `kron(ones(2,3),a)`	`kron(ones((2,3)),a) also tile(a,(2,3))`	Repeat matrix: [ a a a ; a a a ]
`triu(a)`	`triu(a)`	Triangular, upper
`tril(a)`	`tril(a)`	Triangular, lower

Equivalents to “size”

MATLAB/Octave	Python	Description
`size(a)`	`a.shape` or `a.getshape()`	Matrix dimensions
`size(a,2)` or `length(a)`	`a.shape[1]` or `size(a, axis=1)`	Number of columns
`length(a(:))`	`a.size` or `size(a[, axis=None])`	Number of elements
`ndims(a)`	`a.ndim`	Number of dimensions
	`a.nbytes`	Number of bytes used in memory

Matrix- and elementwise- multiplication

MATLAB/Octave	Python	Description
`a .* b`	`a * b` or `multiply(a,b)`	Elementwise operations
`a * b`	`matrixmultiply(a,b)`	Matrix product (dot product)
	`inner(a,b)` or	Inner matrix vector multiplication $a\cdot b’$
	`outer(a,b)` or	Outer product
`kron(a,b)`	`kron(a,b)`	Kronecker product
`a / b`		Matrix division, $b{\cdot}a^{-1}$
`a \ b`	`linalg.solve(a,b)`	Left matrix division, $b^{-1}{\cdot}a$ \newline (solve linear equations)
	`vdot(a,b)`	Vector dot product
	`cross(a,b)`	Cross product

Find; conditional indexing

MATLAB/Octave	Python	Description
`find(a)`	`a.ravel().nonzero()`	Non-zero elements, indices
`[i j] = find(a)`	`(i,j) = a.nonzero()` `(i,j) = where(a!=0)`	Non-zero elements, array indices
`[i j v] = find(a)`	`v = a.compress((a!=0).flat)` `v = extract(a!=0,a)`	Vector of non-zero values
`find(a>5.5)`	`(a>5.5).nonzero()`	Condition, indices
	`a.compress((a>5.5).flat)`	Return values
`a .* (a>5.5)`	`where(a>5.5,0,a)` or `a * (a>5.5)`	Zero out elements above 5.5
	`a.put(2,indices)`	Replace values

Multi-way arrays

MATLAB/Octave	Python	Description
`a = cat(3, [1 2; 1 2],[3 4; 3 4]);`	`a = array([[[1,2],[1,2]], [[3,4],[3,4]]])`	Define a 3-way array
`a(1,:,:)`	`a[0,...]`

File input and output

MATLAB/Octave	Python	Description
`f = load('data.txt')`	`f = fromfile("data.txt")` `f = load("data.txt")`	Reading from a file (2d)
`f = load('data.txt')`	`f = load("data.txt")`	Reading from a file (2d)
`x = dlmread('data.csv', ';')`	`f = load('data.csv', delimiter=';')`	Reading fram a CSV file (2d)
`save -ascii data.txt f`	`save('data.csv', f, fmt='%.6f', delimiter=';')`	Writing to a file (2d)
	`f.tofile(file='data.csv', format='%.6f', sep=';')`	Writing to a file (1d)
	`f = fromfile(file='data.csv', sep=';')`	Reading from a file (1d)

Plotting

Basic x-y plots

MATLAB/Octave	Python	Description
`plot(a)`	`plot(a)`	1d line plot
`plot(x(:,1),x(:,2),'o')`	`plot(x[:,0],x[:,1],'o')`	2d scatter plot
`plot(x1,y1, x2,y2)`	`plot(x1,y1,'bo', x2,y2,'go')`	Two graphs in one plot
`plot(x1,y1)` `hold on` `plot(x2,y2)`	`plot(x1,y1,'o')` `plot(x2,y2,'o')` `show() # as normal`	Overplotting: Add new plots to current
`subplot(211)`	`subplot(211)`	subplots
`plot(x,y,'ro-')`	`plot(x,y,'ro-')`	Plotting symbols and color

Axes and titles

MATLAB/Octave	Python	Description
`grid on`	`grid()`	Turn on grid lines
`axis equal` `axis('equal')` `replot`	`figure(figsize=(6,6))`	1:1 aspect ratio
`axis([ 0 10 0 5 ])`	`axis([ 0, 10, 0, 5 ])`	Set axes manually
`title('title')` `xlabel('x-axis')` `ylabel('y-axis')`		Axis labels and titles
	`text(2,25,'hello')`	Insert text

Log plots

MATLAB/Octave	Python	Description
`semilogy(a)`	`semilogy(a)`	logarithmic y-axis
`semilogx(a)`	`semilogx(a)`	logarithmic x-axis
`loglog(a)`	`loglog(a)`	logarithmic x and y axes

Filled plots and bar plots

MATLAB/Octave	Python	Description
`fill(t,s,'b', t,c,'g')` `% fill has a bug?`	`fill(t,s,'b', t,c,'g', alpha=0.2)`	Filled plot

Functions

MATLAB/Octave	Python	Description
`f = @(x) x.^2;`	`lambda x: x**2`	Anonymous Functions. MATLAB also uses “inline” keyword to construct an inline object. For example inline(‘x^2’). Note that the inline function will be removed from MATLAB in future.
`ezplot(f,[0,40])` `fplot('sin(x/3) - cos(x/5)',[0,40])` `% no ezplot`	`x = np.arange(0,40,.5)` `y = sin(x/3) - cos(x/5)` `plot(x,y, 'o')`	Plot a function for given range

Polar plots

MATLAB/Octave	Python	Description
`theta = 0:.001:2pi;` `r = sin(2theta);`	`theta = arange(0,2pi,0.001)` `r = sin(2theta)`
`polar(theta, rho)`	`polar(theta, rho)`

Histogram plots

MATLAB/Octave	Python	Description
`hist(randn(1000,1))`
`hist(randn(1000,1), -4:4)`
`plot(sort(a))`

3-D Data

Contour and image plots

MATLAB/Octave	Python	Description
`contour(z)`	`levels, colls = contour(Z, V,` `origin='lower', extent=(-3,3,-3,3))` `clabel(colls, levels, inline=1,` `fmt='%1.1f', fontsize=10)`	Contour plot
`contourf(z); colormap(gray)`	`contourf(Z, V,` `cmap=cm.gray,` `origin='lower',` `extent=(-3,3,-3,3))`	Filled contour plot
`image(z)` `colormap(gray)`	`im = imshow(Z,` `interpolation='bilinear',` `origin='lower',` `extent=(-3,3,-3,3))`	Plot image data
	`# imshow() and contour() as above`	Image with contours
`quiver()`	`quiver()`	Direction field vectors

Perspective plots of surfaces over the x-y plane

MATLAB/Octave	Python	Description
`n=-2:.1:2;` `[x,y] = meshgrid(n,n);` `z=x.*exp(-x.^2-y.^2);`	`n=np.arange(-2,2,.1)` `[x,y] =np.meshgrid(n,n)` `z = xpower(math.e,-x2-y*2)`
`mesh(z)`		Mesh plot
`surf(x,y,z)` or `surfl(x,y,z)` `% no surfl()`		Surface plot

Scatter (cloud) plots

MATLAB/Octave	Python	Description
`plot3(x,y,z,'k+')`		3d scatter plot

Save plot to a graphics file

MATLAB/Octave	Python	Description
`plot(1:10)` `print -depsc2 foo.eps` `gset output "foo.eps"` `gset terminal postscript eps` `plot(1:10)`	`savefig('foo.eps')`	PostScript
	`savefig('foo.pdf')`	PDF
	`savefig('foo.svg')`	SVG (vector graphics for www)
`print -dpng foo.png`	`savefig('foo.png')`	PNG (raster graphics)

Data analysis

Set membership operators

MATLAB/Octave	Python	Description
`a = [ 1 2 2 5 2 ];` `b = [ 2 3 4 ];`	`a = array([1,2,2,5,2])` `b = array([2,3,4])` `a = set([1,2,2,5,2])` `b = set([2,3,4])`	Create sets
`unique(a)`	`unique1d(a)` `unique(a)` `set(a)`	Set unique
`union(a,b)`	`union1d(a,b)` `a.union(b)`	Set union
`intersect(a,b)`	`intersect1d(a)` `a.intersection(b)`	Set intersection
`setdiff(a,b)`	`setdiff1d(a,b)` `a.difference(b)`	Set difference
`setxor(a,b)`	`setxor1d(a,b)` `a.symmetric_difference(b)`	Set exclusion
`ismember(2,a)`	`2 in a` `setmember1d(2,a)` `contains(a,2)`	True for set member

Statistics

MATLAB/Octave	Python	Description
`mean(a)`	`a.mean(axis=0)` `mean(a [,axis=0])`	Average
`median(a)`	`median(a)` or `median(a [,axis=0])`	Median
`std(a)`	`a.std(axis=0)` or `std(a [,axis=0])`	Standard deviation
`var(a)`	`a.var(axis=0)` or `var(a)`	Variance
`corr(x,y)`	`correlate(x,y)` or `corrcoef(x,y)`	Correlation coefficient
`cov(x,y)`	`cov(x,y)`	Covariance

Interpolation and regression

MATLAB/Octave	Python	Description
`z = polyval(polyfit(x,y,1),x)` `plot(x,y,'o', x,z ,'-')`	`(a,b) = polyfit(x,y,1)` `plot(x,y,'o', x,a*x+b,'-')`	Straight line fit
`a = x\y`	`linalg.lstsq(x,y)`	Linear least squares $y = ax + b$
`polyfit(x,y,3)`	`polyfit(x,y,3)`	Polynomial fit

Non-linear methods

Polynomials, root finding

MATLAB/Octave	Python	Description
	`poly()`	Polynomial
`roots([1 -1 -1])`	`roots()`	Find zeros of polynomial
`f = inline('1/x - (x-1)')` `fzero(f,1)`		Find a zero near $x = 1$
`solve('1/x = x-1')`		Solve symbolic equations
`polyval([1 2 1 2],1:10)`	`polyval(array([1,2,1,2]),arange(1,11))`	Evaluate polynomial

Differential equations

MATLAB/Octave	Python	Description
`diff(a)`	`diff(x, n=1, axis=0)`	Discrete difference function and approximate derivative
		Solve differential equations

Fourier analysis

MATLAB/Octave	Python	Description
`fft(a)`	`fft(a)` or	Fast fourier transform
`ifft(a)`	`ifft(a)` or	Inverse fourier transform
	`convolve(x,y)`	Linear convolution

Symbolic algebra; calculus

MATLAB/Octave	Python	Description
`factor()`		Factorization

Programming

MATLAB/Octave	Python	Description
`.m`	`.py`	Script file extension
`%` `%` or `#`	`#`	Comment symbol (rest of line)
`% must be in MATLABPATH` `% must be in LOADPATH`	`from pylab import *`	Import library functions
`string='a=234';` `eval(string)`	`string="a=234"` `eval(string)`	Eval

Loops

MATLAB/Octave	Python	Description
`for i=1:5; disp(i); end`	`for i in range(1,6): print(i)`	for-statement
`for i=1:5` `disp(i)` `disp(i*2)` `end`	`for i in range(1,6):` `print(i)` `print(i*2)`	Multiline for statements

Conditionals

MATLAB/Octave	Python	Description
`if 1>0 a=100; end`	`if 1>0: a=100`	if-statement
`if 1>0 a=100; else a=0; end`		if-else-statement

Debugging

MATLAB/Octave	Python	Description
`ans`		Most recent evaluated expression
`whos` or `who`		List variables loaded into memory
`clear x` or `clear [all]`		Clear variable $x$ from memory
`disp(a)`	`print a`	Print

Working directory and OS

MATLAB/Octave	Python	Description
`dir` or `ls`	`os.listdir(".")`	List files in directory
`what`	`grep.grep("*.py")`	List script files in directory
`pwd`	`os.getcwd()`	Displays the current working directory
`cd foo`	`os.chdir('foo')`	Change working directory
`!notepad` `system("notepad")`	`os.system('notepad')` `os.popen('notepad')`	Invoke a System Command

Matlab and Numpy/Python functions side by side

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PYTHON

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