Matlab basics I

Question 1

;

Answer 1

suppresses output of command

Question 2

num2str

Answer 2

converts numbers to a string

Question 3

disp

Answer 3

displays array without printing array name; can also display text

Question 4

figure (x)

Answer 4

causes x to be new figure

Question 5

whos

Answer 5

generates list of variables and arrays in current workspace

Question 6

diary

Answer 6

diary filename: saves all typed commands into “filename”
diary off: suspends input into diary file
diary on: resumes input into diary file

Question 7

size ( )

Answer 7

displays dimension of the array

Question 8

x(1,:)

Answer 8

first row of x

Question 9

x(:,1)

Answer 9

first column of x

Question 10

plot

Answer 10

plot: automatically opens figure window

Question 11

figure

Answer 11

manually opens figure window

Question 12

plot(x)

Answer 12

vectors: plots x vs. its index
matrices: plots columns of x vs their indices

Question 13

plot (x,y)

Answer 13

vectors: plots vector y vs. vector x
matrices: plots rows/columns y vs rows/columns x (whichever line up); generates multiple curves

Question 14

plot(x1, y1, x2, y2)

Answer 14

plots two curves: y1 vs x1 and y2 vs x2

Question 15

plot(x1,y1, ‘r-‘, x2, y2, ‘b–’)

Answer 15

plots y1 vs x1 with a red solid line

plots y2 vs x2 with a blue dashed line

Question 16

title(‘string’)

Answer 16

adds a title to a figure

Question 17

xlabel(‘string’)

ylabel(‘string’)

Answer 17

adds label to x axis

adds label to y axis

Question 18

semilogx(x,y)

Answer 18

plots y vs x using log scale for x and linear scale for y

Question 19

semilogy(x,y)

Answer 19

plots y vs x using linear scale for x and log scale for y

Question 20

loglog(x,y)

Answer 20

plots y vs x using log scale for both axes

Question 21

bar(x)

Answer 21

vector: generates a vertical bar graph of the vector x vs its element index
matrix: groups data by row and generates a group of vertical bars

Question 22

pie (x)

Answer 22

generates a pie chart with every element in x represented by a slice of the pie

Question 23

hist(x)

Answer 23

generates a histogram. computes and plots number of values of x falling into 10 bins (default) equally spaced between min and max values

Question 24

.fig

Answer 24

matlab figure file, can only be opened in matlab

Question 25

print

Answer 25

exports figure plots as graphic images

• deps: create encapsulated postscript image
• djpeg: create a JPEG image
• dtiff: creates a compressed TIFF image
• dpng: create a portable network graphic color image

Question 26

single( )

Answer 26

specifies single precision floating point numbers

Question 27

realmax(‘single’)

realmin(‘single’)

Answer 27

the range of a positive real number of single-precision in MATLAB:

3.4028e+038 and 1.1755e-038

Question 28

int8, int16, int32, int64

Answer 28

signed integers of 8, 16, 32, 64 bits

Question 29

uint8, uint16, uint32, uint64

Answer 29

unsigned integers of 8, 16, 32, 64 bits

Question 30

.*

Answer 30

array multiplication: denotes element-by-element multiplication
arrays must have same dimensions unless one is scalar

Question 31

./

Answer 31

array division: element-by-element division

arrays must have same dimensions unless one is scalar

Question 32

char( )

Answer 32

specifies data type as character

Question 33

single quote

‘ ‘

Answer 33

identifies a character string; each letter/space is treated as an element in an array

Question 34

logical ( )

Answer 34

converts an array of real numeric values into a logical array; non-zero real numbers are true (1) and zero is false (0)

Question 35

input

Answer 35

displays a prompt string and waits for user to type in an input

Question 36

input(‘**’ , ‘s’)

Answer 36

stores input as a string if ‘s’ is the second argument

Question 37

command window

Answer 37

where commands are entered

Question 38

figure window

Answer 38

displays plots and graphs

Question 39

edit window

Answer 39

where you create and modify programs/scripts

also serves as debugger

Question 40

variable

Answer 40

a name representing a chosen value; can assign to be any form of data stored in matlab

Question 41

constant

Answer 41

special kind of variable whose value can’t be changed

Question 42

expression

Answer 42

a combination of operations that produces another value
arithmetic expressions produce an answer
relational expressions produce true (1) or false (0)

Question 43

assignment

Answer 43

variable is assigned a value

Question 44

array

Answer 44

collection of data values in rows and columns

Question 45

m-files

Answer 45

sequences of commands stored in files

“scripts” or “programs”

Question 46

colour coding in edit window

Answer 46

comments: green
variables and numbers: black
complete character strings: pink
incomplete character strings: red
matlab keywords: blue

Question 47

Matlab search path when a name is entered in the command window

Answer 47

1. looks for the name as a variable; displays value
2. looks for name as m-file in current directory; executes the function
3. looks for name as m-file in any directory; executes it

Question 48

workspace

Answer 48

collection of all variables and arrays that can be used by MATLAB when a particular command, M-file, or function is executed.

Question 49

clc

Answer 49

clears command window

Question 50

clear

Answer 50

clears workspace variables

Question 51

clf

Answer 51

clears figure window

Question 52

scalar

Answer 52

1x1 array

Question 53

vector

Answer 53

one dimensional array

Question 54

matrix

Answer 54

two dimensional array

Question 55

variable name restrictions

Answer 55

can only use letters, digits, and underscore.
First character of name must be a letter
case sensitive
can’t use name of predefined constants

Question 56

plotting line type options

Answer 56

• solid
  : dotted
  -. dash-dot
  –dashed

Question 57

plotting point type options

Answer 57

. point
o circle
x x-mark
\+ plus
* star
s square
d diamond
v triangle down
^ triangle up
< triangle left
> triangle right
p pentagram
h hexagram

Question 58

plotting colour type options

Answer 58

b blue
g green
r red
c cyan
m magenta
y yellow
k black

Question 59

types of data stored in matlab

Answer 59

character
logical
numeric
>integer: multiple signed integer types, multiple unsigned integer types
>floating point: single precision and double precision, can store complex and real numbers as either single or double

Question 60

bit

Answer 60

binary digit, either 1 or 0

Question 61

byte

Answer 61

8 bits (8 binary digits that are each either 1 or 0)

Question 62

double( )

Answer 62

specifies double precision floating point data; default type for matlab

Question 63

realmax

realmin

Answer 63

give max and min values of a positive double precision floating point number
1.7977e+308 and 2.2251e-308

Question 64

ASCII

Answer 64

American Standard Code for Information Interchange

seven bit code containing 128 numbers (0-127) each assigned to a character

Question 65

character array

Answer 65

used to store character info in matlab

when creating a vector that contains both character and numeric values, matlab converts all data to character

Question 66

logical array

Answer 66

contains values of 1 or 0 to denote true or false