# Matlab

rename
anandengg's
version from
2018-05-19 08:33

## Section

Question | Answer |
---|---|

exist | Checks for existence of file or variable. |

global | Declares variables to be global. |

lookfor | Searches help entries for a keyword. |

quit | Stops MATLAB. |

who | Lists current variables. |

whos | Lists current variables (long display). |

cd | Changes current directory. |

date | Displays current date. |

delete | Deletes a file. |

diary | Switches on/off diary file recording. |

dir | Lists all files in current directory. |

load | Loads workspace variables from a file. |

path | Displays search path. |

pwd | Displays current directory. |

save | Saves workspace variables in a file. |

type | Displays contents of a file. |

what | Lists all MATLAB files in the current directory. |

wklread | Reads .wk1 spreadsheet file. |

Question | Answer |
---|---|

\n | Insert a new line in the output string. |

\t | Insert a tab in the output string. |

format short | Four decimal digits (default). |

format long | 16 decimal digits. |

format short e | Five digits plus exponent. |

format long e | 16 digits plus exponents. |

format bank | Two decimal digits. |

format + | Positive, negative, or zero. |

format rat | Rational approximation. |

format compact | Suppresses some line feeds. |

format loose | Resets to less compact display mode. |

Question | Answer |
---|---|

cat | Concatenates arrays. |

find | Finds indices of nonzero elements. |

length | Computes number of elements. |

linspace | Creates regularly spaced vector. |

logspace | Creates logarithmically spaced vector. |

max | Returns largest element. |

min | Returns smallest element. |

Question | Answer |
---|---|

prod | Product of each column. |

reshape | Changes size. |

size | Computes array size. |

sort | Sorts each column. |

sum | Sums each column. |

eye | Creates an identity matrix. |

ones | Creates an array of ones. |

zeros | Creates an array of zeros. |

cross | Computes matrix cross products. |

dot | Computes matrix dot products. |

det | Computes determinant of an array. |

inv | Computes inverse of a matrix. |

pinv | Computes pseudoinverse of a matrix. |

rank | Computes rank of a matrix. |

rref | Computes reduced row echelon form. |

cell | Creates cell array. |

celldisp | Displays cell array. |

cellplot | Displays graphical representation of cell array.J |

num2cell | Converts numeric array to cell array. |

deal | Matches input and output lists. |

iscell | Identifies cell array. |

Question | Answer |
---|---|

axis | Sets axis limits. |

fplot | Intelligent plotting of functions. |

grid | Displays gridlines. |

plot | Generates xy plot. |

Prints plot or saves plot to a file. | |

title | Puts text at top of plot. |

xlabel | Adds text label to x-axis. |

ylabel | Adds text label to y-axis. |

axes | Creates axes objects. |

close | Closes the current plot. |

close all | Closes all plots. |

figure | Opens a new figure window. |

gtext | Enables label placement by mouse. |

hold | Freezes current plot. |

legend | Legend placement by mouse. |

refresh | Redraws current figure window. |

set | Specifies properties of objects such as axes. |

subplot | Creates plots in subwindows. |

text | Places string in figure. |

bar | Creates bar chart. |

loglog | Creates log-log plot. |

polar | Creates polar plot. |

semilogx | Creates semilog plot. (logarithmic abscissa). |

semilogy | Creates semilog plot. (logarithmic ordinate). |

stairs | Creates stairs plot. |

stem | Creates stem plot. |

## clear Removes variables from memory.

exist Checks for existence of file or variable.

global Declares variables to be global.

help Searches for a help topic.

lookfor Searches help entries for a keyword.

quit Stops MATLAB.

who Lists current variables.

whos Lists current variables (long display).

## Special Variables and Constants

ans Most recent answer.

eps Accuracy of floating-point precision.

i,j The imaginary unit -1.

Inf Infinity.

NaN Undefined numerical result (not a number).

pi The number p .

System and File Commands

cd Changes current directory.

date Displays current date.

delete Deletes a file.

diary Switches on/off diary file recording.

dir Lists all files in current directory.

load Loads workspace variables from a file.

path Displays search path.

pwd Displays current directory.

save Saves workspace variables in a file.

type Displays contents of a file.

what Lists all MATLAB files in the current directory.

wklread Reads .wk1 spreadsheet file.

## Input/Output and Formatting Commands

Input/Output Commands

disp Displays contents of an array or string.

fscanf Read formatted data from a file.

format Controls screen-display format.

fprintf Performs formatted writes to screen or file.

input Displays prompts and waits for input.

; Suppresses screen printing.

## Vector, Matrix and Array Commands

cat Concatenates arrays.find Finds indices of nonzero elements.

length Computers number of elements.

linspace Creates regularly spaced vector.

logspace Creates logarithmically spaced vector.

max Returns largest element.

min Returns smallest element.

prod Product of each column.

reshape Change size

size Computes array size.

sort Sorts each column.

sum Sums each column.

Special Matrices

eye Creates an identity matrix.

ones Creates an array of ones.

zeros Creates an array of zeros.

Matrix Arithmetic

cross Computes cross products.

dot Computes dot products.

Matrix Commands for Solving Linear Equations

det Computes determinant of an array.

inv Computes inverse of a matrix.

pinv Computes pseudoinverse of a matrix.

rank Computes rank of a matrix.

rref Computes reduced row echelon form.

## Cell Array Functions

cell Creates cell array.celldisp Displays cell array.

cellplot Displays graphical representation of cell array.

Question | Answer |
---|---|

num2cel | l Converts numeric array to cell array. |

deal | Matches input and output lists. |

Question | Answer |
---|---|

Structure | Functions |

fieldnames | Returns field names in a structure array. |

getfield | Returns field contents of a structure array. |

isfield | Identifies a structure array field. |

isstruct | Identifies a structure array. |

rmfield | Removes a field from a structure array. |

setfield | Sets contents of field. |

struct | Creates structure array. |

## Plotting Commands

Basic xy Plotting Commands

axis Sets axis limits.

fplot Intelligent plotting of functions.

grid Displays gridlines.

plot Generates xy plot.

print Prints plot or saves plot to a file

title Puts text at top of plot.

xlabel Adds text label to x-axis.

ylabel Adds text label to y-axis.

Plot Enhancement Commands

axes Creates axes objects.

close Closes the current plot.

close all Closes all plots.

figure Opens a new figure window.

gtext Enables label placement by mouse.

hold Freezes current plot.

legend Legend placement by mouse.

refresh Redraws current figure window.

set Specifies properties of objects such as axes.

subplot Creates plots in subwindows.

text Places string in figure.

Specialized Plot Commands

bar Creates bar chart.

loglog Creates log-log plot.

polar Creates polar plot.

semilogx Creates semilog plot (logarithmic abscissa).

semilogy Creates semilog plot (logarithmic ordinate).

stairs Creates stairs pot.

stem Creates stem plot.

## Three-Dimensional Plotting Commands

contour Creates contour plot.

mesh Creates three-dimensional mesh surface plot.

meshc Same as mesh with contour plot underneath.

meshz Same as mesh with vertical lines underneath.

plot3 Creates three-dimensional plots from lines and points.

surf Creates shaded three-dimensional mesh surface plot.

surfc Same as surf with contour plot underneath.

meshgrid Creates rectangular grid.

waterfall Same as mesh with mesh lines in one direction.

zlabel Adds text label to z-axis.

Histogram Functions

bar Creates a bar chart.

hist Aggregates the data into equally spaced bins.

histc Aggregates the data into unequally spaced bins.

## Programming Logical and Relational Operators

### Relational operator : equal to.

Question | Answer |
---|---|

~= Relational operator | not equal to. |

< Relational operator | less than. |

<= Relational operator | less than or equal to. |

> Relational operator | greater than. |

& Logical operator: AND.

| Logical operator: OR.

~ Logical operator: NOT.

xor Logical operator: EXCLUSIVE OR.

Program Flow Control

break Terminates execution of a loop.

case Provides alternate execution paths within switch structure.

else Delineates alternate block of statements.

elseif Conditionally executes statements.

end Terminates for, while, and if statements.

error Display error messages.

for Repeats statements a specific number of times

if Executes statements conditionally.

otherwise Default part of switch statement.

return Return to the invoking function.

switch Directs program execution by comparing point with case expressions.

warning Display a warning message.

while Repeats statements an indefinite number of times.

## Logical Functions

any True if any elements are nonzero.

all True if all elements are nonzero.

find Finds indices of nonzero elements.

finite True if elements are finite.

isnan True if elements are undefined.

isinf True if elements are infinite.

isempty True if matrix is empty.

isreal True if all elements are real.

eval Interpret strings containing Matlab expressions.

feval Function evaluation.

function Creates a user-defined function M-file.

global Define global variables.

nargin Number of function input arguments.

nargout Number of function output arguments.

script Script M-files

Timing

cputime CPU time in seconds.

clock Current date and time as date vector.

tic, toc Start, stop a stopwatch timer.

## Mathematical Functions Exponential and Logarithmic Functions

exp(x) Exponential; ex.

log(x) Natural logarithm; ln(x).

log10(x) Common (base 10) logarithm; log(x)= log10(x).

sqrt(x) Square root; x.

Hyperbolic Functions

Question | Answer |
---|---|

acosh(x) | Inverse hyperbolic cosine; cosh –1 (x). |

acoth(x) | Inverse hyperbolic cotangent; coth –1 (x). |

acsch(x) | Inverse hyperbolic cosecant; csch –1 (x). |

asech(x) | Inverse hyperbolic secant; sech –1 (x). |

asinh(x) | Inverse hyperbolic sine; sinh –1 (x). |

atanh(x) | Inverse hyperbolic tangent; tanh –1 (x). |

cosh(x) | Hyperbolic cosine; cosh(x). |

coth(x) | Hyperbolic cotangent; cosh(x)/sinh(x). |

csch(x) | Hyperbolic cosecant; 1/sinh(x). |

sech(x) | Hyperbolic secant; 1/cosh(x). |

sinh(x) | Hyperbolic sine; sinh(x). |

tanh(x) | Hyperbolic tangent; sinh(x)/cosh(x). |

Complex Functions

Question | Answer |
---|---|

abs(x) | Absolute value; |x|. |

angle(x) | Angle of a complex number x. |

conj(x) | Complex conjugate of x. |

imag(x) | Imaginary part of a complex number x. |

real(x) | Real part of a complex number x. |

Statistical Functions

Question | Answer |
---|---|

erf(x) | Computes the error function erf (x). |

mean | Calculates the average. |

median | Calculates the median. |

std | Calculates the standard deviation. |

Random Number Functions

Question | Answer |
---|---|

rand | Generates uniformly distributed random numbers between 0 and 1. |

randn | Generates normally distributed random numbers. |

Numeric Functions

Question | Answer |
---|---|

ceil | Rounds to the nearest integer toward •. |

fix | Rounds to the nearest integer toward zero. |

floor | Rounds to the nearest integer toward - •. |

round | Rounds towards the nearest integer. |

sign | Signum function. |

## String Functions

Question | Answer |
---|---|

findstr | Finds occurrences of a string. |

strcmp | Compares strings. |

char | Creates character string array |

## Polynomial and Regression Functions

Question | Answer |
---|---|

conv | Computes product of two polynomials |

deconv | Computes ratio of polynomials. |

eig | Computes the eigenvalues of a matrix. |

poly | Computes polynomial from roots. |

polyfit | Fits a polynomial to data. |

polyval | Evaluates polynomial and generates error estimates. |

roots | Computes polynomial roots. |

Interpolation Functions

Question | Answer |
---|---|

interp1 | Linear and cubic-spline interpolations of a function of one variable. |

interp2 | Linear interpolation of a function of two variables. |

spline | Cubic-spline interpolation. |

unmkpp | Computes the coefficients of cubic-spine polynomials. |

Root | Finding and Minimization |

fmin | Finds minimum of single-variable function. |

fmins | Finds minimum of multivariable function. |

fzero | Finds zero of single-variable function. |

Numerical Integration Functions

Question | Answer |
---|---|

quad | Numerical integration with adaptive Simpson’s rule. |

quadl | Numerical integration with adaptive Lobatto quadrature. |

trapz | Numerical integration with the trapezoidal rule. |

diff(x) | Computes the difference between adjacent elements in the vector x. |

polyder | Differentiates a polynomial, a polynomial product, or a polynomial quotient. |

ODE Solvers

Question | Answer |
---|---|

ode23 | Nonstiff, low-order solver. |

ode45 | Nonstiff, medium-order solver. |

ode113 | Nonstiff, variable-order solver. |

ode23s | Stiff, low-order. |

ode23t | Moderately stiff, trapezoidal rule solver. |

ode23b | Stiff, low-order solver. |

ode15s | Stiff, variable-order solver. |

odeset | Creates integrator options structure for ODE solvers. |

Predefined | Input Functions |

gensig | Generates a periodic sine, square, or pulse input. |

sawtooth | Generates a periodic sawtooth input. |

square | Generates a square wave input. |

stepfun | Generates a step function input. |

Functions for Creating and Evaluating Symbolic Expressions

Question | Answer |
---|---|

class | Returns the class of an expression. |

digits | Sets the number of decimal digits used to do variable precision arithmetic. |

double | Converts an expression to numeric form. |

ezplot | Generates a plot of a symbolic expression. |

findsym | Finds the symbolic variables in a symbolic expression. |

numden | Returns the numerator and denominator of an expression. |

sym | Creates a symbolic variable. |

syms | Creates one or more symbolic variables. |

vpa | Sets the number of digits used to evaluate expressions. |

Functions for Manipulating Symbolic Expressions

Question | Answer |
---|---|

collect | Collects coefficients of like powers in an expression. |

expand | Expands an expression by carrying out jpowers. |

factor | Factors an expression. |

poly2sym | Converts a polynomial coefficient vector to a symbolic polynomial. |

pretty | Displays an expression in a form that resembles typeset mathematics. |

simple | Searches for the shortest form of an expression. |

simplify | Simplifies an expression using Maple’s simplification rules. |

subs | Substitutes variables or expressions. |

sym2poly | Converts an expression to a polynomial coefficient vector. |

Symbolic Calculus Functions

Question | Answer |
---|---|

diff | Returns the derivative of an expression. |

Dirac | Dirac delta function (unit impulse). |

Heaviside | Heaviside function (unit step). |

int | Returns the integral of an expression. |

limit | Returns the limit of an expression. |

symsum | Returns the symbolic summation of an expression. |

taylor | Returns the Taylor series of a function. |

Symbolic Solution of Algebraic and Transcendental Equations

Question | Answer |
---|---|

solve | Solves symbolic equations. |

Symbolic | Solution of Differential Equations |

dsolve | Returns a symbolic solution of a differential equation or set of equations. |

Laplace | Transform Functions |

ilaplace | Returns the inverse Laplace transform. |

laplace | Returns the Laplace transform. |

Symbolic | Linear Algebra Functions |

det | Returns the determinant of a matrix. |

eig | Returns the eigenvalues (characteristic roots) of a matrix. |

inv | Returns the inverse of a matrix. |

poly | Returns the characteristic polynomial of a matrix. |

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