Matlab

Question 1

Is matlab compiled or interpreted?

Answer 1

Interpreted, this means it can be run interactively with scripts and by calling functions

Question 2

clc

Answer 2

clear the command window

Question 3

clear

Answer 3

clear the workspace (erase all variables from memory)

Question 4

clear var_name

Answer 4

erase variable var_name from memory

Question 5

help fcn_name

Answer 5

get basic information about fcn_name

Question 6

What would A(: , 2) return?

Answer 6

The 2nd column of A

Question 7

What would A(4 , :) return?

Answer 7

The 4th row of A

Question 8

What would A(:, 2:3) return?

Answer 8

The 2nd and 3rd columns of A

Question 9

Where does indexing start in Matlab?

Answer 9

At 1

Question 10

How do we define character arrays?

Answer 10

With single quotes, for example ‘ENAS130’

Question 11

What happens if you try to multiply a character array by a scalar?

Answer 11

The ASCII values of the elements of the character array would be multiplied by the scalar

Question 12

What does size() return?

Answer 12

Returns the number of rows and columns

Question 13

What does length() return?

Answer 13

Returns the length of the largest array dimension

Question 14

What does height()/width() return?

Answer 14

Height returns number of rows, width returns number of columns

Question 15

How do you save data into a .mat file?

Answer 15

save(filename) will save all variables and values currently in the workspace to a .mat file

Question 16

How do you load data from a .mat file?

Answer 16

load(‘filename’, ‘variables’) if wanting to load specific varaibles, else load filename.mat

Question 17

How do you view file contents without loading them in?

Answer 17

whos -file filename

Question 18

How do you save info to a .dat file?

Answer 18

save filename.dat -ascii var1 var2, or without var1 and var2 if you want to save all variables

Question 19

How do you load data from a .dat file?

Answer 19

load filename.dat -ascii

Question 20

How do you use colon notation?

Answer 20

initVal : step : endVal

Question 21

How do you use the linspace function?

Answer 21

linspace(initVal, endVal, length of vector)

Question 22

How can you easily initialize a vector of equal values?

Answer 22

x = scalar * ones(1,3)

Question 23

What does max return?

Answer 23

returns the maximum value and its index

Question 24

What does polyfit do?

Answer 24

finds the best-fit line coefficients

Question 25

What does polyval do?

Answer 25

evaluates the best-fit line

Question 26

What does sum do?

Answer 26

Sums all the elements across a row vector, or down a column

Question 27

How do you use find()?

Answer 27

To get the indices of elements equal to a certain integer, find(myArray==3)

Question 28

How do you use unique()?

Answer 28

To list unique elements in increasing order, unique(myArray)

Question 29

How do you use any()?

Answer 29

To test if at least one element equals a certain int, returns 1 if true, 0 if false. any(myArray==3)

Question 30

How do you use all()?

Answer 30

To test if all elements equal a certain int, all(myArray==3)

Question 31

What does input do?

Answer 31

get user input from the command window

Question 32

What does disp do?

Answer 32

displays unformatted output

Question 33

What does num2str do?

Answer 33

converts numbers to strings

Question 34

What does sprintf do?

Answer 34

create formatted strings (without displaying)

Question 35

What does fprintf do?

Answer 35

prints formatted info to the command window

Question 36

What does fscanf do?

Answer 36

reads formatted info from a file

Question 37

What is the syntax for fopen?

Answer 37

fopen(filename, access_type). the access type if 'wt' if writing to a file, 'rt' if reading from a file

Question 38

When using fprintf, what would be returned if printing 8 doubles with a \n?

Answer 38

72, 8 bytes for every double and 8 for each \n

Question 39

In what cases is a semicolon needed?

Answer 39

when assigning a value or returning information from a function

Question 40

What is the matlab equivalent of !=?

Answer 40

~=

Question 41

What is the matlab equivalent of &&?

Answer 41

&

Question 42

If a function is defined in the same file that it is used, where must it be defined?

Answer 42

After the script that calls it?

Question 43

If a function is defined in another file, what are the constraints?

Answer 43

only one function per file, file must be in the same folder or path, and the filename must be fcn_name.m

Question 44

How do you use fprintf?

Answer 44

fprintf(fileID, format, data) example: fprintf(outputFile, '%f\n', matrix1)