R-Matlab-Python 유의어 Published by onesixx 20-07-26 20-07-26
R for MATLAB users
Help
R/S-Plus MATLAB/Octave Description help.start() doc Browse help interactively help() help help or doc doc Help on using help help(plot) or ?plot help plot Help for a function help(package=’splines’) help splines or doc splines Help for a toolbox/library package demo() demo Demonstration examples example(plot) Example using a function
Searching available documentation
R/S-Plus MATLAB/Octave Description help.search(‘plot’) lookfor plot Search help files apropos(‘plot’) Find objects by partial name library() help List available packages find(plot) which plot Locate functions methods(plot) List available methods for a function
Using interactively
R/S-Plus MATLAB/Octave Description Rgui octave -q Start session source(‘foo.R’) foo(.m) Run code from file history() history Command history savehistory(file=”.Rhistory”) diary on [..] diary off Save command history q(save=’no’) exit or quit End session
Operators
R/S-Plus MATLAB/Octave Description help(Syntax) help – Help on operator syntax
Arithmetic operators
R/S-Plus MATLAB/Octave Description a<-1; b<-2 a=1; b=2; Assignment; defining a number a + b a + b Addition a – b a – b Subtraction a * b a * b Multiplication a / b a / b Division a ^ b a .^ b Power, $a^b$ a %% b rem(a,b) Remainder a %/% b Integer division factorial(a) factorial(a) Factorial, $n!$
Relational operators
R/S-Plus MATLAB/Octave Description a == b a == b Equal a < b a < b Less than a > b a > b Greater than a <= b a <= b Less than or equal a >= b a >= b Greater than or equal a != b a ~= b Not Equal
Logical operators
R/S-Plus MATLAB/Octave Description a && b a && b Short-circuit logical AND a || b a || b Short-circuit logical OR a & b a & b or and(a,b) Element-wise logical AND a | b a | b or or(a,b) Element-wise logical OR xor(a, b) xor(a, b) Logical EXCLUSIVE OR !a ~a or not(a)or !a Logical NOT any(a) True if any element is nonzero all(a) True if all elements are nonzero
root and logarithm
R/S-Plus MATLAB/Octave Description sqrt(a) sqrt(a) Square root log(a) log(a) Logarithm, base $e$ (natural) log10(a) log10(a) Logarithm, base 10 log2(a) log2(a) Logarithm, base 2 (binary) exp(a) exp(a) Exponential function
Round off
R/S-Plus MATLAB/Octave Description round(a) round(a) Round ceil(a) ceil(a) Round up floor(a) floor(a) Round down fix(a) Round towards zero
Mathematical constants
R/S-Plus MATLAB/Octave Description pi pi $\pi=3.141592$ exp(1) exp(1) $e=2.718281$
Missing values; IEEE-754 floating point status flags
R/S-Plus MATLAB/Octave Description NaN Not a Number Inf Infinity, $\infty$
Complex numbers
R/S-Plus MATLAB/Octave Description 1i i Imaginary unit z <- 3+4i z = 3+4i A complex number, $3+4i$ abs(3+4i) or Mod(3+4i) abs(z) Absolute value (modulus) Re(3+4i) real(z) Real part Im(3+4i) imag(z) Imaginary part Arg(3+4i) arg(z) Argument Conj(3+4i) conj(z) Complex conjugate
Trigonometry
R/S-Plus MATLAB/Octave Description atan2(b,a) atan(a,b) Arctangent, $\arctan(b/a)$
Generate random numbers
R/S-Plus MATLAB/Octave Description runif(10) rand(1,10) Uniform distribution runif(10, min=2, max=7) 2+5*rand(1,10) Uniform: Numbers between 2 and 7 matrix(runif(36),6) rand(6) Uniform: 6,6 array rnorm(10) randn(1,10) Normal distribution
Vectors
R/S-Plus MATLAB/Octave Description a <- c(2,3,4,5) a=[2 3 4 5]; Row vector, $1 \times n$-matrix adash <- t(c(2,3,4,5)) adash=[2 3 4 5]’; Column vector, $m \times 1$-matrix
Sequences
R/S-Plus MATLAB/Octave Description seq(10) or 1:10 1:10 1,2,3, … ,10 seq(0,length=10) 0:9 0.0,1.0,2.0, … ,9.0 seq(1,10,by=3) 1:3:10 1,4,7,10 seq(10,1) or 10:1 10:-1:1 10,9,8, … ,1 seq(from=10,to=1,by=-3) 10:-3:1 10,7,4,1 seq(1,10,length=7) linspace(1,10,7) Linearly spaced vector of n=7 points rev(a) reverse(a) Reverse a(:) = 3 Set all values to same scalar value
Concatenation (vectors)
R/S-Plus MATLAB/Octave Description c(a,a) [a a] Concatenate two vectors c(1:4,a) [1:4 a]
Repeating
R/S-Plus MATLAB/Octave Description rep(a,times=2) [a a] 1 2 3, 1 2 3 rep(a,each=3) 1 1 1, 2 2 2, 3 3 3 rep(a,a) 1, 2 2, 3 3 3
Miss those elements out
R/S-Plus MATLAB/Octave Description a[-1] a(2:end) miss the first element a[-10] a([1:9]) miss the tenth element a[-seq(1,50,3)] miss 1,4,7, … a(end) last element a(end-1:end) last two elements
Maximum and minimum
R/S-Plus MATLAB/Octave Description pmax(a,b) max(a,b) pairwise max max(a,b) max([a b]) max of all values in two vectors v <- max(a) ; i <- which.max(a) [v,i] = max(a)
Vector multiplication
R/S-Plus MATLAB/Octave Description a*a a.*a Multiply two vectors dot(u,v) Vector dot product, $u \cdot v$
Matrices
R/S-Plus MATLAB/Octave Description rbind(c(2,3),c(4,5)) a = [2 3;4 5] Define a matrix
Concatenation (matrices); rbind and cbind
R/S-Plus MATLAB/Octave Description rbind(a,b) [a ; b] Bind rows cbind(a,b) [a , b] Bind columns [a(:), b(:)] Concatenate matrices into one vector rbind(1:4,1:4) [1:4 ; 1:4] Bind rows (from vectors) cbind(1:4,1:4) [1:4 ; 1:4]’ Bind columns (from vectors)
Array creation
R/S-Plus MATLAB/Octave Description matrix(0,3,5) or array(0,c(3,5)) zeros(3,5) 0 filled array matrix(1,3,5) or array(1,c(3,5)) ones(3,5) 1 filled array matrix(9,3,5) or array(9,c(3,5)) ones(3,5)*9 Any number filled array diag(1,3) eye(3) Identity matrix diag(c(4,5,6)) diag([4 5 6]) Diagonal magic(3) Magic squares; Lo Shu
Reshape and flatten matrices
R/S-Plus MATLAB/Octave Description matrix(1:6,nrow=3,byrow=T) reshape(1:6,3,2)’; Reshaping (rows first) matrix(1:6,nrow=2) reshape(1:6,2,3); Reshaping (columns first) as.vector(t(a)) a'(:) Flatten to vector (by rows, like comics) as.vector(a) a(:) Flatten to vector (by columns) a[row(a) <= col(a)] vech(a) Flatten upper triangle (by columns)
Shared data (slicing)
R/S-Plus MATLAB/Octave Description b = a b = a Copy of a
Indexing and accessing elements (Python: slicing)
R/S-Plus MATLAB/Octave Description a <- rbind(c(11, 12, 13, 14), a = [ 11 12 13 14 … Input is a 3,4 array a[2,3] a(2,3) Element 2,3 (row,col) a[1,] a(1,:) First row a[,1] a(:,1) First column a([1 3],[1 4]); Array as indices a[-1,] a(2:end,:) All, except first row a(end-1:end,:) Last two rows a(1:2:end,:) Strides: Every other row a[-2,-3] All, except row,column (2,3) a[,-2] a(:,[1 3 4]) Remove one column
Assignment
R/S-Plus MATLAB/Octave Description a[,1] <- 99 a(:,1) = 99 a[,1] <- c(99,98,97) a(:,1) = [99 98 97]’ a[a>90] <- 90 a(a>90) = 90; Clipping: Replace all elements over 90
Transpose and inverse
R/S-Plus MATLAB/Octave Description t(a) a’ Transpose a.’ or transpose(a) Non-conjugate transpose det(a) det(a) Determinant solve(a) inv(a) Inverse ginv(a) pinv(a) Pseudo-inverse norm(a) Norms eigen(a)$values eig(a) Eigenvalues svd(a)$d svd(a) Singular values chol(a) Cholesky factorization eigen(a)$vectors [v,l] = eig(a) Eigenvectors rank(a) rank(a) Rank
Sum
R/S-Plus MATLAB/Octave Description apply(a,2,sum) sum(a) Sum of each column apply(a,1,sum) sum(a’) Sum of each row sum(a) sum(sum(a)) Sum of all elements apply(a,2,cumsum) cumsum(a) Cumulative sum (columns)
Sorting
R/S-Plus MATLAB/Octave Description a = [ 4 3 2 ; 2 8 6 ; 1 4 7 ] Example data t(sort(a)) sort(a(:)) Flat and sorted apply(a,2,sort) sort(a) Sort each column t(apply(a,1,sort)) sort(a’)’ Sort each row sortrows(a,1) Sort rows (by first row) order(a) Sort, return indices
Maximum and minimum
R/S-Plus MATLAB/Octave Description apply(a,2,max) max(a) max in each column apply(a,1,max) max(a’) max in each row max(a) max(max(a)) max in array i <- apply(a,1,which.max) [v i] = max(a) return indices, i pmax(b,c) max(b,c) pairwise max apply(a,2,cummax) cummax(a)
Matrix manipulation
R/S-Plus MATLAB/Octave Description a[,4:1] fliplr(a) Flip left-right a[3:1,] flipud(a) Flip up-down rot90(a) Rotate 90 degrees kronecker(matrix(1,2,3),a) repmat(a,2,3) Repeat matrix: [ a a a ; a a a ] a[lower.tri(a)] <- 0 triu(a) Triangular, upper a[upper.tri(a)] <- 0 tril(a) Triangular, lower
Equivalents to “size”
R/S-Plus MATLAB/Octave Description dim(a) size(a) Matrix dimensions ncol(a) size(a,2) or length(a) Number of columns prod(dim(a)) length(a(:)) Number of elements ndims(a) Number of dimensions object.size(a) Number of bytes used in memory
Matrix- and elementwise- multiplication
R/S-Plus MATLAB/Octave Description a * b a .* b Elementwise operations a %*% b a * b Matrix product (dot product) outer(a,b) or a %o% b Outer product crossprod(a,b) or t(a) %*% b Cross product kronecker(a,b) kron(a,b) Kronecker product a / b Matrix division, $b{\cdot}a^{-1}$ solve(a,b) a \ b Left matrix division, $b^{-1}{\cdot}a$ \newline (solve linear equations)
Find; conditional indexing
R/S-Plus MATLAB/Octave Description which(a != 0) find(a) Non-zero elements, indices which(a != 0, arr.ind=T) [i j] = find(a) Non-zero elements, array indices ij <- which(a != 0, arr.ind=T); v <- a[ij] [i j v] = find(a) Vector of non-zero values which(a>5.5) find(a>5.5) Condition, indices ij <- which(a>5.5, arr.ind=T); v <- a[ij] Return values a .* (a>5.5) Zero out elements above 5.5
Multi-way arrays
R/S-Plus MATLAB/Octave Description a = cat(3, [1 2; 1 2],[3 4; 3 4]); Define a 3-way array a(1,:,:)
File input and output
R/S-Plus MATLAB/Octave Description f <- read.table(“data.txt”) f = load(‘data.txt’) Reading from a file (2d) f <- read.table(“data.txt”) f = load(‘data.txt’) Reading from a file (2d) f <- read.table(file=”data.csv”, sep=”;”) x = dlmread(‘data.csv’, ‘;’) Reading fram a CSV file (2d) write(f,file=”data.txt”) save -ascii data.txt f Writing to a file (2d)
Plotting
Basic x-y plots
R/S-Plus MATLAB/Octave Description plot(a, type=”l”) plot(a) 1d line plot plot(x[,1],x[,2]) plot(x(:,1),x(:,2),’o’) 2d scatter plot plot(x1,y1, x2,y2) Two graphs in one plot plot(x1,y1) plot(x1,y1) Overplotting: Add new plots to current subplot(211) subplots plot(x,y,type=”b”,col=”red”) plot(x,y,’ro-‘) Plotting symbols and color
Axes and titles
R/S-Plus MATLAB/Octave Description grid() grid on Turn on grid lines plot(c(1:10,10:1), asp=1) axis equal 1:1 aspect ratio plot(x,y, xlim=c(0,10), ylim=c(0,5)) axis([ 0 10 0 5 ]) Set axes manually plot(1:10, main=”title”, title(‘title’) Axis labels and titles
Log plots
R/S-Plus MATLAB/Octave Description plot(x,y, log=”y”) semilogy(a) logarithmic y-axis plot(x,y, log=”x”) semilogx(a) logarithmic x-axis plot(x,y, log=”xy”) loglog(a) logarithmic x and y axes
Filled plots and bar plots
R/S-Plus MATLAB/Octave Description plot(t,s, type=”n”, xlab=””, ylab=””) fill(t,s,’b’, t,c,’g’) Filled plot stem(x[,3]) Stem-and-Leaf plot
Functions
R/S-Plus MATLAB/Octave Description f <- function(x) sin(x/3) – cos(x/5) f = inline(‘sin(x/3) – cos(x/5)’) Defining functions plot(f, xlim=c(0,40), type=’p’) ezplot(f,[0,40]) Plot a function for given range
Polar plots
R/S-Plus MATLAB/Octave Description theta = 0:.001:2*pi; polar(theta, rho)
Histogram plots
R/S-Plus MATLAB/Octave Description hist(rnorm(1000)) hist(randn(1000,1)) hist(rnorm(1000), breaks= -4:4) hist(randn(1000,1), -4:4) hist(rnorm(1000), breaks=c(seq(-5,0,0.25), seq(0.5,5,0.5)), freq=F) plot(apply(a,1,sort),type=”l”) plot(sort(a))
3d data
Contour and image plots
R/S-Plus MATLAB/Octave Description contour(z) contour(z) Contour plot filled.contour(x,y,z, contourf(z); colormap(gray) Filled contour plot image(z, col=gray.colors(256)) image(z) Plot image data quiver() Direction field vectors
Perspective plots of surfaces over the x-y plane
R/S-Plus MATLAB/Octave Description f <- function(x,y) x*exp(-x^2-y^2) n=-2:.1:2; persp(x,y,z, mesh(z) Mesh plot persp(x,y,z, surf(x,y,z) or surfl(x,y,z) Surface plot
Scatter (cloud) plots
R/S-Plus MATLAB/Octave Description cloud(z~x*y) plot3(x,y,z,’k+’) 3d scatter plot
Save plot to a graphics file
R/S-Plus MATLAB/Octave Description postscript(file=”foo.eps”) plot(1:10) PostScript pdf(file=’foo.pdf’) PDF devSVG(file=’foo.svg’) SVG (vector graphics for www) png(filename = “Rplot%03d.png” print -dpng foo.png PNG (raster graphics)
Data analysis
Set membership operators
R/S-Plus MATLAB/Octave Description a <- c(1,2,2,5,2) a = [ 1 2 2 5 2 ]; Create sets unique(a) unique(a) Set unique union(a,b) union(a,b) Set union intersect(a,b) intersect(a,b) Set intersection setdiff(a,b) setdiff(a,b) Set difference setdiff(union(a,b),intersect(a,b)) setxor(a,b) Set exclusion is.element(2,a) or 2 %in% a ismember(2,a) True for set member
Statistics
R/S-Plus MATLAB/Octave Description apply(a,2,mean) mean(a) Average apply(a,2,median) median(a) Median apply(a,2,sd) std(a) Standard deviation apply(a,2,var) var(a) Variance cor(x,y) corr(x,y) Correlation coefficient cov(x,y) cov(x,y) Covariance
Interpolation and regression
R/S-Plus MATLAB/Octave Description z <- lm(y~x) z = polyval(polyfit(x,y,1),x) Straight line fit solve(a,b) a = x\y Linear least squares $y = ax + b$ polyfit(x,y,3) Polynomial fit
Non-linear methods
Polynomials, root finding
R/S-Plus MATLAB/Octave Description polyroot(c(1,-1,-1)) roots([1 -1 -1]) Find zeros of polynomial f = inline(‘1/x – (x-1)’) Find a zero near $x = 1$ solve(‘1/x = x-1’) Solve symbolic equations polyval([1 2 1 2],1:10) Evaluate polynomial
Differential equations
R/S-Plus MATLAB/Octave Description diff(a) Discrete difference function and approximate derivative Solve differential equations
Fourier analysis
R/S-Plus MATLAB/Octave Description fft(a) fft(a) Fast fourier transform fft(a, inverse=TRUE) ifft(a) Inverse fourier transform
Symbolic algebra; calculus
R/S-Plus MATLAB/Octave Description factor() Factorization
Programming
R/S-Plus MATLAB/Octave Description .R .m Script file extension # %or # Comment symbol (rest of line) library(RSvgDevice) % must be in MATLABPATH Import library functions string <- “a <- 234” string=’a=234′; Eval
Loops
R/S-Plus MATLAB/Octave Description for(i in 1:5) print(i) for i=1:5; disp(i); end for-statement for(i in 1:5) { for i=1:5 Multiline for statements
Conditionals
R/S-Plus MATLAB/Octave Description if (1>0) a <- 100 if 1>0 a=100; end if-statement if 1>0 a=100; else a=0; end if-else-statement ifelse(a>0,a,0) Ternary operator (if?true:false)
Debugging
R/S-Plus MATLAB/Octave Description .Last.value ans Most recent evaluated expression objects() whos or who List variables loaded into memory rm(x) clear x or clear [all] Clear variable $x$ from memory print(a) disp(a) Print
Working directory and OS
R/S-Plus MATLAB/Octave Description list.files() or dir() dir or ls List files in directory list.files(pattern=”\.r$”) what List script files in directory getwd() pwd Displays the current working directory setwd(‘foo’) cd foo Change working directory system(“notepad”) !notepad Invoke a System Command
Time-stamp: “2007-11-09T16:46:36 vidar”©2006 Vidar Bronken Gundersen, /mathesaurus.sf.net
