Matlab - scripts

Question 1

what does the “if” command mean when writing scripts?

Answer 1

if an expression is true, the next command will execute

Question 2

what does the else command mean

Answer 2

• it often follows the if command
• if an expression is false or 0, an else command will execute the following lines of script
• must have an end

Question 3

what does this line of code mean?
» A = 10;
if (A>5)
B = 1
else
B = 0
end
B = 1

Answer 3

if a (10) is greater than 5 then b equals 1. else if a (10) is not greater than 5, b will be 0.

Question 4

what does the command for loop mean?

Answer 4

it will run a set of commands multiples times in a loop.

Question 5

what are the rules for “for” loops

Answer 5

• a loop will have a counter how many times it has run through the loop
• the counter can be used within the loop as an index or a variable
• must always have an end

Question 6

what is the code for a loop to run once?

Answer 6

i = 1

Question 7

what would this code give?
for i=1:4
A(i) = i*2
end

Answer 7

A = 2
A = 2 4
A = 2 4 6
A = 2 4 6 8

Question 8

what does this code mean?
for i=1:3
mdat(i) = mean(data(cat==i))
end

Answer 8

We put the counter i in the place of the number which changed between each line
and the loop will calculate the mean for each category and put the results in mdat.

Question 9

Put the value you want to match in brackets after the switch statement. Each____ is a possibility, and if the value matches, then next statement will execute. It none of the cases match, the lines after _______ will execute. A____ must have an end to tell it to stop.

Answer 9

case
otherwise
switch

Question 10

what is a switch loop?

Answer 10

is like testing lots of ifs one after the other. It is useful if you want to match a value to
several alternatives

Question 11

Switch loops can also determine if one text string matches another text
string, and are useful for classifying text strings.

Question 12

what would this code give us?
A = 3;
switch(A)
case 1
disp ‘A is one’
case 3
disp ‘A is three’
case 5
disp ‘A is five’
otherwise
disp ‘A is not one or three or five’
end

Answer 12

A is three

Question 13

what is a while command

Answer 13

a while command is like a for loop which will keep going until It gets to a false value

Question 14

what does this while loop code mean?
x = 1;
y = -5;
while (x==1)
y = y+1
if (y>1)
x = 2
end
end

Answer 14

the loop keeps increasing y until y is greater than 1. Then x is set to 2, so the loop stops.

Question 15

what is a catch statement used for?

Answer 15

it is used for catching errors in the script and prevent them from crashing It.
example:
» A = 1:10;
» B = 1:5;
for i=1:length(A)
try
C(i) = A(i) + B(i) %% this will give an error when i
%% is greater than the length of B
catch
disp(‘B is too small’)
end
end
C = 2
C = 2 4
C = 2 4 6
C = 2 4 6 8
C = 2 4 6 8 10
B is too small