Matlab Cheat Sheet Built in functions/ 1415 Some nifty commands ting point accu i) i1/ix/f1d at e Cell co contain any variable type all va e() Strings s and regular exp command dist Logical operators AND. -Circuit or ity 5t0 Keyb ard short re (5) edito isvecto id5 n(A)) ang errors oc riable generatio ,use RREF hrough instead:ine(A) p/dovr inspace(a.b.n) R/T aN(a.b) s(a.B) wind d of x nax window /re
Matlab Cheat Sheet Some nifty commands clc Clear command window clear Clear system memory clear x Clear x from memory commandwindow open/select commandwindow whos lists data structures whos x size, bytes, class and attributes of x ans Last result close all closes all figures close(H) closes figure H winopen(pwd) Open current folder class(obj) returns objects class save filename saves all variables to .mat file save filename x,y saves x,y variables to .mat file save -append filename x appends x to .mat file load filename loads all variables from .mat file ver Lists version and toolboxes beep Makes the beep sound doc function Help/documentation for function docsearch string search documentation web google.com opens webadress inputdlg Input dialog box methods(A) list class methods for A Statistical commands distrnd random numbers from dist distpdf pdf from dist distcdf cdf dist distrnd random numbers from dist hist(x) histogram of x histfit(x) histogram and *Standard distributions (dist): norm, t, f, gam, chi2, bino *Standard functions: mean,median,var,cov(x,y),corr(x,y), *quantile(x,p) is not textbook version. (It uses interpolation for missing quantiles. Keyboard shortcuts edit filename Opens filename in editor Alt Displays hotkeys F1 Help/documentation for highlighted function F5 Run code F9 Run highlighted code F10 Run code line F11 Run code line, enter functions Shift+F5 Leave debugger F12 Insert break point Ctrl+Page up/down Moves between tabs Ctrl+shift Moves between components Ctrl+C Interrupts code Ctrl+D Open highlighted codes file Ctrl+ R/T Comment/uncomment line Ctrl+N New script Ctrl+W Close script Ctrl+shift+d Docks window Ctrl+shift+u Undocks window Ctrl+shift+m max window/restore size Built in functions/constants abs(x) absolute value pi 3.1415... inf ∞ eps floating point accuracy 1e6 106 sum(x) sums elements in x cumsum(x) Cummulative sum prod Product of array elements cumprod(x) cummulative product diff Difference of elements round/ceil/fix/floor Standard functions.. *Standard functions: sqrt, log, exp, max, min, Bessel *Factorial(x) is only precise for x ,>=,5)=5 changes some values T.Properties.Varnames Variable names T = array2table(A) ! make table from array T = innerjoin(T1,T2) innerjoin T = outerjoin(T1,T2) outerjoin ! Rows and vars indicate rows and variables. tables are great for large datasets, because they use less memory and allow faster operations. *rowfun is great for tables, much faster than eg. looping matrix and vector operations/functions x=[1, 2, 3] 1x3 (Row) vector x=[1; 2; 3] 3x1 (Column) vector x=[1, 2; 3, 4] 2x2 matrix x(2)=4 change index value nr 2 x(:) All elements of x (same as x) x(j:end) j’th to last element of x x(2:5) 2nd to 5th element of x x(j,:) all j row elements x(:,j) all j column elements diag(x) diagonal elements of x x.*y Element by element multiplication x./y Element by element division x+y Element by element addition x-y Element by element subtraction A^n normal/Matrix power of A A.^n Elementwise power of A A’ Transpose inv(A) Inverse of matrix size(x) Rows and Columns eye(n) Identity matrix sort(A) sorts vector from smallest to largest eig(A) Eigenvalues and eigenvectors numel(A) number of array elements x(x>5)=0 change elemnts >5 to 0 x(x>5) list elements >5 find(A>5) Indices of elements >5 find(isnan(A)) Indices of NaN elements [A,B] concatenates horizontally [A;B] concatenates vertically For functions on matrices, see bsxfun,arrayfun or repmat *if arrayfun/bsxfun is passed a gpuArray, it runs on GPU. *Standard operations: rank,rref,kron,chol *Inverse of matrix inv(A) should almost never be used, use RREF through \ instead: inv(A)b = A\b
Plotting commands 2aepa.tanasokNerea5,ummeuicalnatho if(criteria 1) if criteria 1 is true do procedure 1 re figi plot(,y) 2.) line elseif(criteria 2) .else if criteria 2 is true do procedure 2 fminsearch(任un,xo) minimum of unconstrained multivariable function o1aprocedr else do procedure 3 set(figl,'color','red') line color (see ethod set(fig1. rker size (see mple:Constrained log-likelihood maximizatior note the Parms_est-fmincon(@(Parms)-flogL(Parms,x1,x2,x3.y) switch svitch_expression if case n holds InitialGuess,,.,,LvrBound,UprBound,) case If none bolds graphics object j giot(a...) Debbuging etc procedure 2 get e handle figures in single plot starts thmer end procedure 3 xlabel('\mu line','FontSize',14) names x/y/z axis toc stops timer ylim(a b]) profile on starts proffler General comments title('name','fontsize',22) egend Location rid to plot y/c adds legends asingly larger portions hold on dbstop if error stops at first de try/catch block Saves time hold off rsbreakp .Trick:Program that (1)takes a long time to run and (2) doesnt use all of the CPU/memory ?-split it into more lasterr Last error message set(h,'WindowStyle','Docked'); programs and run using different workers (instances). Docked window lastvarn Last warning message .Matlab is a column vector hase y break for/we p memory for variables,Matlab requires contiguous memory not sp do all in event queue Data import/export a yellow,black You can turn the standard (mostly)Just-In-Time Load/save sascii text files (txt.csv) compilation of using:leature accel ol ◆Sore1 ine sty1es plot(x,y,'b--o') load/save matlab files (.m) nread/imrite Image files Output commands Dlanlavs 4 dieits after 0 lays 15 digits after 0 Programming commands Functions defined in a m file is only avallable there. Displays the string x king function disp(x) disp(x Displays the string x Graphic cards(GPU)'s 111 DETEN USEDI in x to string function [y1,. ·,y]。myfn(x1..,x) s.1f(1) um2str(a)]) mat2str(x) Converts the matrix in x to string computations can be independent.Consider using the GPU! f2:un()yfu(x3,2 System commands Conditionals and loops ath to for i-1:n th(string) existent row/column.Good practise:Use 3i rat 【ha for imag Makes new directory use ==for comparine doubles they are floatine point mporary directory while(criteria) precision for example:0.01 ==(1-0.99)=0. list folder content or Nie lists toolboxes (.com) ver
Plotting commands fig1 = plot(x,y) 2d line plot, handle set to fig1 set(fig1, ’LineWidth’, 2) change line width set(fig1, ’LineStyle’, ’-’) dot markers (see *) set(fig1, ’Marker’, ’.’) marker type (see *) set(fig1, ’color’, ’red’) line color (see *) set(fig1, ’MarkerSize’, 10) marker size (see *) set(fig1, ’FontSize’, 14) fonts to size 14 figure new figure window figure(j) graphics object j get(j) returns information graphics object j gcf(j) get current figure handle subplot(a,b,c) Used for multiple figures in single plot xlabel(’\mu line’,’FontSize’,14) names x/y/z axis ylim([a b]) Sets y/x axis limits for plot to a-b title(’name’,’fontsize’,22) names plot grid on/off; Adds grid to plot legend(’x’,’y’,’Location’,’Best’) adds legends hold on retains current figure when adding new stuff hold off restores to default (no hold on) set(h,’WindowStyle’,’Docked’); Docked window style for plots datetick(’x’,yy) time series axis plotyy(x1,y1,x2,y2) plot on two y axis refreshdata refresh data in graph if specified source drawnow do all in event queue * Some markers: ’, +, *, x, o, square * Some colors: red, blue, green, yellow, black * color shortcuts: r, b, g, y, k * Some line styles: -, --, :, -. * shortcut combination example: plot(x,y,’b--o’) Output commands format short Displays 4 digits after 0 format long Displays 15 digits after 0 disp(x) Displays the string x disp(x) Displays the string x num2str(x) Converts the number in x to string num2str([’nA is = ’ OFTEN USED! num2str(a)]) ! mat2str(x) Converts the matrix in x to string int2str(x) Converts the integer in x to string sprintf(x) formated data to a string System commands addpath(string) adds path to workspace genpath(string) gets strings for subfolders pwd Current directory mkdir Makes new directory tempdir Temporary directory inmem Functions in memory exit Close matlab dir list folder content ver lists toolboxes Nonlinear nummerical methods quad(fun,a,b) simpson integration of @fun from a to b fminsearch(fun,x0) minimum of unconstrained multivariable function using derivative-free method fmincon minimum of constrained function Example: Constrained log-likelihood maximization, note the - Parms_est = fmincon(@(Parms) -flogL(Parms,x1,x2,x3,y) ,InitialGuess,[],[],[],[],LwrBound,UprBound,[]); Debbuging etc. keyboard Pauses exceution return resumes exceution tic starts timer toc stops timer profile on starts profiler profile viewer Lets you see profiler output try/catch Great for finding where errors occur dbstop if error stops at first error inside try/catch block dbclear clears breakpoints dbcont resume execution lasterr Last error message lastwarn Last warning message break Terminates executiion of for/while loop waitbar Waiting bar Data import/export xlsread/xlswrite Spreadsheets (.xls,.xlsm) readtable/writetable Spreadsheets (.xls,.xlsm) dlmread/dlmwrite text files (txt,csv) load/save -ascii text files (txt,csv) load/save matlab files (.m) imread/imwrite Image files Programming commands return Return to invoking function exist(x) checks if x exists G=gpuArray(x) Convert varibles to GPU array function [y1,...,yN] = myfun(x1,...,xM) Anonymous functions not stored in main programme myfun = @(x1,x2) x1+x2; or even using myfun2 = @myfun(x) myfun(x3,2) Conditionals and loops for i=1:n procedure Iterates over procedure end incrementing i from 1 to n by 1 while(criteria) procedure Iterates over procedure end as long as criteria is true(1) if(criteria 1) if criteria 1 is true do procedure 1 procedure1 elseif(criteria 2) ,else if criteria 2 is true do procedure 2 procedure2 else , else do procedure 3 procedure3 end switch switch_expression if case n holds, case 1 run procedure n. If none holds procedure 1 run procedure 3 case 2 (if specified) procedure 2 otherwise procedure 3 end General comments • Monte-Carlo: If sample sizes are increasing generate largest size first in a vector and use increasingly larger portions for calculations. Saves time+memory. • Trick: Program that (1) takes a long time to run and (2) doesnt use all of the CPU/memory ? - split it into more programs and run using different workers (instances). • Matlab is a column vector based language, load memory columnwise first always. For faster code also prealocate memory for variables, Matlab requires contiguous memory usage!. Matlab uses copy-on-write, so passing pointers (adresses) to a function will not speed it up. Change variable class to potentially save memory (Ram) using: int8, int16, int32, int64, double, char, logical, single • You can turn the standard (mostly) Just-In-Time compilation off using: feature accel off. You can use compiled (c,c++,fortran) functions using MEX functions. • Avoid global variables, they user-error prone and compilers cant optimize them well. • Functions defined in a .m file is only available there. Preface function names with initials to avoid clashes, eg. MrP function1. • Graphic cards(GPU)’s have many (small) cores. If (1) program is computationally intensive (not spending much time transfering data) and (2) massively parallel, so computations can be independent. Consider using the GPU! • Using multiple cores (parallel computing) is often easy to implement, just use parfor instead of for loops. • Warnings: empty matrices are NOT overwritten ([] + 1 = []). Rows/columns are added without warning if you write in a nonexistent row/column. Good practise: Use 3i rather than 3*i for imaginary number calculations, because i might have been overwritten by earlier. 1/0 returns inf, not NaN. Dont use == for comparing doubles, they are floating point precision for example: 0.01 == (1 − 0.99) = 0. Copyright c 2015 Thor Nielsen (thorpn86@gmail.com) http://www.econ.ku.dk/pajhede/
