matlab week 1.2

Question 1

vectors

Answer 1

one dimensional collection of variables written between brackets []

Question 2

[1 2 3 4 5 ]

Answer 2

row vector

Question 3

[1; 2; 3; 4; 5]

Answer 3

column vector

Question 4

size(x)

Answer 4

returns dimensions of row (two values, n by m)

Question 5

length(x)

Answer 5

returns number of elements in a vector (one value)

Question 6

linspace

Answer 6

generates row vector of n points between and including two points

Question 7

y = linspace(a, b, n)
what does each letter represent?

Answer 7

y is the created row vector
a is the starting number, included
b is the end number, included (if it fits in increment)
n is the number of points generated

Question 8

linspace(1,5)

Answer 8

returns 1 by 100 vector between 1 and 5

Question 9

default ‘n’ if not specified by linspace function

Answer 9

100

Question 10

linspace(1, 5, 1)

Answer 10

5
you generated one number between 1 and 5 so it took a stepsize of 5

Question 11

t = [1 2 3]
y = log(t)
what is y?

Answer 11

y = [ log(1), log(2), log(3) ]

Question 12

element wise operations

Answer 12

use dot
.* ./ .^

Question 13

transpose

Answer 13

converts column vector into a row vector and vice versa (‘)

Question 14

a = [ 1 2 3]
a’

Answer 14

a =
1
2
3

Question 15

b = [ 1, 2, 3, 4 + i]
b’

Answer 15

b =
1
2
3
4 - i

Question 16

b = [ 1 2 3 4+i]
b.’

Answer 16

b =
1
2
3
4 + i

Question 17

zeros and ones function

Answer 17

zeros -> creates n by m matrix filled with 0s
ones -> creates n by m matrix filled with 1s

Question 18

ones(3)

Answer 18

1 1 1
1 1 1
1 1 1

Question 19

zeros(2, 3)

Answer 19

0 0 0
0 0 0

Question 20

rand function

Answer 20

generates matrix with random numbers between 0 and 1

Question 21

rand(3)

Answer 21

random 0-1 matrix of 3 by 3 dims

Question 22

randi(10,1,5)

Answer 22

randomly generates 10 integer numbers (whole numbers) between 1 and 5

Question 23

writing mathmatical equations in matlab

Answer 23

use the roots function with value as coefficient and index as the root

Question 24

6e^-10t

Answer 24

6 * exp(-10 * t)

Question 25

save FileName a b

Answer 25

saves variables a and b to the file FileName.mat

Question 26

load FileName

Answer 26

loads variables in FileName.mat into the wordkspace

Question 27

fid = fopen(filename, permission)

Answer 27

filename is the name of file
permission:
‘r’ for open file for reading
‘w’ for open file for writing

Question 28

uigetfile

Answer 28

standard open file dialog box

Question 29

[newfile, newpath] = uigetfile(‘.’, ‘Select File’)

Answer 29

used to save the data in .txt format and set path

newfile is the name of the new file
newpath is where the file is stored on your computer

Question 30

cd(newpath)

Answer 30

changes the current directory

Question 31

format specs
fprint(fid, format, A…)
format: % 6.3f % 6.3f /n

Answer 31

%_# -> space after percent means insert space before the value in file
6 is the field width, 6 numbers in total printed
3 is the precision, 3 points after decimal
f means floating point number

repeated to signify format spec for number of columns in matrix