MATLAB Cheat Sheet
Miscellaneous useful notes
1. Text after a percent sign (
%
) represent
comments
, and are ignored by the code.
2. Text in parentheses is evaluated by MATLAB prior to other text, in a manner identically to how parentheses
are treated in math.
3. The two basic windows in MATLAB for the user to work in are the
Command Window
and the
Editor
.
The Command Window is for quick commands that the user wishes to see executed; it acts out one line of
code at a time, and prints the result unless that result is suppressed by the user. The Editor is for writing
larger pieces of code in the form of functions or scripts, both of which are described toward the end of this
document.
4. To suppress printing of command output, a simicolon (
;
) can be placed after the command. E.g.,
x=4
will
assign the value
4
to
x
, and print
x=4
to the screen.
x=4;
will assign the value
4
to
x
, without printing
x=4
to the screen.
5. To clear variable assignments, type
clear nameOfVariable
. E.g.,
clear x
will make it so that
x
no longer
has any assigned value. To do this for all variables, type
clear all
.
Data types
The most important data types in MATLAB are
doubles
,
strings
, and
Booleans
; these are MATLAB's default
numeric, text, and logical data types. Below, examples of each of these are given -
doub1
and
doub2
are doubles,
str1
and
str2
are strings, and
boo1
and
boo2
are Booleans.
doub1=3.0;doub2=1;
str1='hello';str2='h';
boo1=false;boo2=5>2;
Arrays
An
array
is a list of data types. It can be multidimensional, though MATLAB works most easily with 1- and
2-dimensional arrays. Arrays can be dened with in several ways. Below,
r1
and
r2
each represent a single-row
array -
r1
is dened explicitly, and
r2
is dened with a handy MATLAB notation.
c1
and
c2
are similarly dened
single-column arrays.
M1
is a 2-dimensional array.
r1=[1,2,3,4,5]%Commas to separate entries in an array within a row.
r2=1:2:9%This is equivalent to writing r2=[1,3,5,7,9]. The notation is start:step:stop.
%A notation start:stop can also be used, which simply means start:1:stop.
c1=[1;2;3;4;5]%semicolons to separate rows.
c2=(1:2:9)'%The ' symbol means "transpose", i.e., switch the role of rows and columns.
M1=[1,2,3;4,5,6;7,8,9]%M1 is a 2-dimensional array.
To select an element of an array, the format is
ArrayName(index)
for a 1D array, and
ArrayName(rowIndex,colIndex)
for a 2D array. The lowest array
index
in MATLAB arrays is the number 1.
r2(2)%Gives 3, since the second entry in r2 is 3.
c2(4)%Gives 7, since the fourth entry in r2 is 3.
M1(3,2)%Gives 8, since M1(3) is [7,8,9] and [7,8,9](2) is 8.
Finally, arrays can be
concatenated
, which means added onto. In the other direction,
subarrays
of a given array
can be selected. There are variations on both of these operations, but the most basic form of each is demonstrated
below - more detail can be found online.
rbig=cat(2,r1,r2)%cat(2,array1,array2) concatenates array1 and array2 row-wise.
%This gives rbig=[1,2,3,4,5,1,3,5,7,9].
cbig=cat(1,c1,c2)%cat(1,array1,array2) concatenates the two specified arrays column-wise.
%This gives cbig=[1;2;3;4;5;1;3;5;7;9].
r2small=r2(2:4)%r2small=[3,5,7].
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