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Matlab Quick Command Reference Sheet: Page 1 Information commands : help Lists topics on which help is available help Bob Lists documentation on the command Bob.m if it exists lookfor Bob Search all m-files for keyword “Bob” doc Bob Display HTML documentation on the keyword “Bob” Workspace Commands: who Lists variables currently in the workspace whos Lists variables currently in workspace, with size clear Clears the workspace of all variables clear a Clears only variable a from workspace clear x y z Clears variables x,y, and z from workspace save Bob Saves current workspace as Bob.mat file save Bob x y Saves current variables x and y as file Bob.mat load Bob Load workspace with variables from Bob.mat File and Directory Commands: what List m-files, mat-files, and mex-files in current directory dir Lists all files and folders in current directory ls Lists all files and folders in current directory. delete Bob Deletes file Bob type Bob Lists the contents of m-file Bob.m format short Changes to short number display format format long Changes to long number display format format long e Changes to long exponential number display format format compact Changes to tightly spaced format format loose Changes to loosely spaced format pwd Display name of current directory cd Display name of current directory cd Bob Changes to dir Bob in current directory cd a:\student\Bob Changes to dir Bob in A:\student\ directory cd .. Change to directory above the current one. clc Clears command window path Displays the current path definition echo Displays commands executing from an M-file diary on Appends screen output to file diary. diary Bob Appends screen output to file Bob. diary off Turns off appending of screen out. diary Toggle switch to turn diary on/off. Termination commands: Ctrl-c Abort commands or program run back to Matlab prompt. quit Exits Matlab exit Exits Matlab
General system commands: Page 2 info Displays general Matlab information computer Displays computer type date Displays date as text clock Displays time as number array [yr, mth, day, hr, min, sec] more Controls the paged output according to screen size tic Starts a stop watch toc Stops a stop watch Predefined Variables: ans Holds the result of the last unnamed expression or calculation eps Smallest numerical difference between two different real numbers inf Value of infinity Inf Value of infinity NaN Value of 0 / 0 pi Value of 3.14159...... i Value of - j Value of - realmin Smalles usable positive real number realmax Largest useable positive real number nargin Number of function input arguments nargout Number of function output arguments Simple Graphics Commands: plot(x,y) Plots array y vs. array x plot(x,y,’*b’) Plots array y vs. array x with blue ’s plot(x,y,’b’,x,z,’-r’) Plots y vs. x and z vs. x on same graph grid Creates a grid background on graph xlabel(‘x axis label’) Labels x axis ylabel(‘y axis label’) Labels y axis title(‘title name’) Puts title on plot text(gx,gy,’string’) Places text ‘string’ at position (gx,gy) on graph gtext(‘string’) Prompts user to pick mouse point to place ‘string’ legend(‘string1’,’string2’, ...) Creates legend of multiple plot lines on graph axis ([xmin xmax ymin ymax]) Manually sets axis limits axis auto Automatically sets axis limits (default) axis square Fixes graph in square shape axis equal Fixes graph to equal x and y increments axis normal Resets graph to default mode whitebg(‘r’) Change graph background color to red hold on Freezes current graph for appending other plots to it. hold off Removes freeze to plot shg Shows graphic window clg Clears graphic window close Closes the graphic window
Trigonometric functions : (Trig function use radians, not degrees) Page 4 cos(x) cosine of x sin(x) sine of x tan(x) tangent of x asin(x) arcsine of x acos(x) arccosine of x atan(x) 2 quadrant arctangent of x atan2(x,y) 4 quadrant arctangent of x and y sinh(x) hyperbolic sine of x cosh(x) hyperbolic cosine of x tanh(x) hyperbolic tangent of x asinh(x) hyperbolic arcsine of x acosh(x) hyperbolic arccosine of x Common Math Functions: abs(x) absolute value of x exp(x) exponential operation, ex imag(s) computes imaginary part of complex value s log(x) natural logarithm log10(x) base 10 logarithm real(x) compute real part of complex number rem(x,y) computes remainder of division for x/y sign(x) generates -1, 0, or 1 based on sign of x sqrt(x) square root of x ceil(x) round x toward +infinity fix(x) round x toward zero floor(x) round x toward -infinity round(x) round x to nearest integer Statistical Functions: ( A refers to a 2D matrix, v refers to a 1D array) max(A) returns row vector with max of each column of matrix A max(v) returns scalar value with maximum of vector v min(A) returns row vector with min of each column of matrix A min(v) returns scalar value with minimum of vector v mean(A) returns row vector with mean of each column of matrix A mean(v) returns scalar value with mean of vector v median(A) returns row vector with median of each column of matrix A median(v) returns scalar value with median of vector v sort(A) sorts each column of A in ascending order sort(v) sorts vector v in ascending order sum(A) returns row vector with sum of each column of matrix A sum(v) returns scalar value with sum of vector v prod(A) returns row vector with product of each column of matrix A prod(v) ) returns scalar value with product of vector v cumprod(A) determines cumulative product matrix cumsum(A) determines cumulative sum matrix
Page 5 Logical functions: (refers to V is a vector, A is a matrix, t is a text string ) all(V) Returns 1 if all elements of vector V are nonzero, 0 if not all zero any(V) Returns 1 if any element of vector V is nonzero, 0 if none zero find(V) Returns vector of indices of nonzero elements all(A) For each column of matrix A, returns 1 if all the elements in each column are nonzero, 0 if not. any(A) For each column in matrix A, returns 1 if any of the elements in each column are nonzero, 0 if none are nonzero. find(A) Returns a column vector of indices of nonzero elements exist(‘t’) Checks if string t is either a variable, function, or file. Brings back 0 if it does not exist, 1 if a variable, 2 if an m-file, 3 if a mex-file, 4 if Simulink, or 5 if a built-in Matlab function. finite(A) Returns matrix of size A with 1s for finite values, 0s for Inf or NaN isinf(A) Returns matrix of size A with 1s for Inf or -Inf values, 0s if not isempty(A) Returns 1 for an empty matrix, [], 0 is not empty ishold Returns 1 if ‘hold plot’ is ON isletter(t) Returns 1s where t is letters, 0s where t is not alphabetic isnan(A) Returns matrix of size A with 1’s for NaNs, 0 where values are not NaN isreal(A) Returns 1 if all elements are real, 0 is any is not real isstr(x) Returns 1 if is character string, 0 is not a string logical(A) converts a numerical matrix to a logical matrix where 0 is false, ~0 is true Utility matrices and matrix fucntions: (m,n are integers, v is vector, A is a matrix) linspace(x,y,m) linearly spaced vector from x to y with m points logspace(x,y,m) logrithmic spaced vector from x to y with m points eye(m,n) returns an mn identity matrix magic(m) returns an mm magic square with integers from 1 to m^ zeros(m,n) returns an mn matrix of zeros ones(m,n) returns an mn matrix of ones rand(m,n) returns an mn matrix of random numbers between 0 and 1 randn(m,n) returns an mn matrix of normally distributed random numbers diag(v) generates a diagonal matrix with v as the diagonal diag(A) extracts the diagonal of matrix A as a vector length(V) returns length of vector V size(A) returns size of matrix A as vector [#of row, # of col] rot90(A) rotates matrix A by 90 degrees fliplr(A) flips matrix A from left to right flipud(A) flips matrix A from up to down tril(A) extracts lower triangular part of A triu(A) extracts upper triangular part of A rank(A) determine the rank of matrix A rref(A) returns reduced row echelon form of matrix A det(A) returns the determinant of square matrix A inv(A) returns the inverse of a square, nonsingular matrix A norm(A) returns norm of a matrix A norm(v) returns norm of a vector v cond(A) returns condition number of matrix A [L,U,P]=lu(A) extract the LU decomposition and permutation matrix P [V,D]=eig(A) finds eigenvectors,V and eigenvalues D of matrix A
if-Statement Structure: Page 7 if (a<0) % general structure of if-statement. logical comparators. x = 1 %calculation when if true < > <= >= = = ~= end %if % closing statement of if statement if-elseif-else Statment Structure:. logical operators. if (a<0) % general structure of if-statement ~ NOT x=1 % calculation for if true & AND elseif(a>0) % elseif general statement | OR x=2 % calculation for elseif true xor(A,B) Exclusive OR else % else statement x=3 % calculation when no if or elseif is true end %if % closing statement of if statement while Loop Structure: while (k>0) % enter loop when while statement is true k=k-1 % calculation when while is true end %while % closing statement of while statement for Loop Structure: for k=1:n % enter for loop, where k =first:increment:last x=x+5 % calculation if (x>100) % secondary condition to exit loop break % send program to statement following end%for end %if %closing statement of if end %for % closing statement of for switch-case-otherwise Statement Structure: switch flag % set switch flag where flag is a number (usually integer) case value1 % use this case if flag = = value x=x+1 % calculations for case 1 case value2 % use this case if flag = = value x = x+2 % calculations for case 2 case value3 % use this case if flag = = value x = x+3 % calculations for case 3 otherwise % use this case if flag ~= any value# x = 0 % calculations for case otherwise end %case % closing statement for switch Other loop and if related commands : break breaks out of inner most for or while loop, goes to line following end%loop return returns control to calling program keyboard active pause, allows checking of variable values, to continue type return error(‘display message’) displays user defined error message and stops program execution pause pauses program until user hits Enter pause(5) pauses program for 5 seconds
File Access Commands: fid = fopen(‘filename.ext’,’permission’) Opens file with name filename.ext , fclose(fid) Close file. frewind(fid) Reset file pointer to beginning of file. A=fscanf(fid,’%f’) Read floating point numbers from file storing values into column matrix A until all numbers have been read. B=fscanf(fid,’%f’, 6) Read 6 floating point numbers from file storing values into column matrix B [A,count]=fscanf(fid,’%f’,[2,inf]) Read floating point numbers from file storing them in 2xN matrix A until all values have been read. fprintf(fid,’%f \n’, B) Write all values of B matrix into the file, one item per line. fprintf(fid,’%f %f %f \n’, a,b,c) Write values a, b, and c into the file on same line.
Example of using fscanf to read in values of x and y from data file: Bob.dat on A drive. this gives x = [1 2 3 4 5] and y = [5 10 15 25 20]
Example used to read long one dimensional array of unknown size in file: data.txt The data gets stored in the column vector A and the variable count is the number of data values read.
Example used to write the values of x and y arrays into a file called MyData.txt When completed the written file will look like Bob.dat 1 5 2 10 3 15 4 25 5 20 MyData.txt starts here: 1.0000 5. 2.0000 10. 3.0000 35. 4.0000 50. 5.0000 100. permissions: ‘w’ write file ‘r’ read file ‘a’ append file fidBob=fopen(‘A:Bob.dat’,’r’) A=fscanf(fidBob,’%f%f ‘,[2,5]) x = A(1,1:end) y = A(2,1:end) fclose(fidBob) fidA=fopen(‘data.txt’,’r’) [A,count]=fscanf(fidA,’%f’) fclose(fidA) x = [1 2 3 4 5] y = [ 5 10 35 50 100] fidMy=fopen(‘MyData.txt’,’w’) fprintf(fidMy,’MyData.txt starts here:’) for i=1:length(x) fprintf(fidMy,’ %8.4f %f \n’, x(i), y(i)) end %for fclose(fidMy)
