# Some basic MATLAB questions

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Okay, so I'm just starting to use MATLAB for engineering assignments. The assignment from my instructor requires us to write a loop using if, else if and else commands. Thats not what I have trouble with, but I need some assistance to come up with a way to take a number and assign it a letter grade based on the number. So the grading scale is like this:

0-59 - F 60-69 - D 70-79 - C 80-89 - B 90-100 - A

So I know I will start the first condition with if, but could someone do an example to show me how it is supposed to be set up? Please DO NOT do the whole thing, as I want to learn it on my own, but sometimes we need a bit of assistance.

Thank you

EDIT: Thanks to Matt for the first Question.

##### 1 Comment

Naftali
on 18 Feb 2013

Edited: Walter Roberson
on 18 Feb 2013

% n - input numbers in array

% g - output grades

grades = 'FDCBA' ;

k = min(max(floor(0.1*(n-50)+1,1),5) ;

g = grades(k) ;

### Accepted Answer

Matt Fig
on 11 Sep 2012

Edited: Matt Fig
on 11 Sep 2012

X = round(rand*6)

if X<3

disp('Small X')

elseif X==3

disp('X is 3')

elseif X>=3 & X<5

disp('Medium X')

else

disp('X is 5 or 6')

end

##### 1 Comment

nejib
on 21 Aug 2023

hello :

i need to have the the same amplitude!!!!

any help : !!

>> t = 0:1/1e3:10;

d = [0:2:60;sin(1*pi*0.1*(0:2:60))]';

x = @rectpuls;

y = pulstran(t,d,x);

plot(t,y)

hold off

xlabel('Time (s)')

ylabel('Waveform')

>>

### More Answers (9)

Matt Tearle
on 11 Sep 2012

Thank you for your asking such a great question! Matt has basically given you all the info you need for this assignment, but, in the spirit of Sean's "not what you were asked, but some cool stuff you should know about MATLAB"...

x = randi(100,20,1) % Make some grades

y = char(70*ones(size(x))); % Everyone gets an F!

y(x>59) = 'D' % Upgrade the Ds (and better)

y(x>69) = 'C' % Upgrade the Cs

y(x>79) = 'B' % The Bs

y(x>89) = 'A' % And finally the As

Or (requires Stats TB, which you should have as a student)

y = ordinal(x,{'F','D','C','B','A'},[],[0,60:10:100])

hist(y) % See the grades

pie(hist(y)) % Grade distribution

mean(x(y>='C')) % The average score of those who got a C or better

##### 1 Comment

Matt Fig
on 11 Sep 2012

Edited: Matt Fig
on 11 Sep 2012

As per requested:

% x is the numerical unknown grade

G = char(interp1([-inf,59,60,69,70,79,80,89,90,inf],['FFDDCCBBAA'],x,'n'))

or, for 2012+ versions:

G = char(interp1([-realmax,59,60,69,70,79,80,89,90,realmax],double(['FFDDCCBBAA']),x,'n'))

##### 0 Comments

Matt Fig
on 11 Sep 2012

Edited: Matt Fig
on 11 Sep 2012

Another one-liner (short!):

% x is the unknown numerical grade.

G = char(65+sum(x<.5+[59 59:10:89]));

As it stands it only works for scalar x. BSXFUN would cure that if it was needed, like so.

G = char(65+sum(bsxfun(@lt,x,.5+[59 59:10:89].')));

##### 0 Comments

Sean de Wolski
on 11 Sep 2012

Edited: Sean de Wolski
on 11 Sep 2012

I know this is not the purpose of your assignment, but here is a cool way to do it. The logic should be easily transmittable to if/else/etc instead of histc()

letters = 'FDCBA';

grade = 87

[~,idx] = histc(grade,[0 59:10:89 100+eps(100)]);

letters(idx)

##### 5 Comments

Matt Fig
on 11 Sep 2012

Jan
on 11 Sep 2012

index = max(1, ceil(-4.9:0.1:5.1));

pool = 'FDCBAA';

Grade = pool(index(x + 1));

##### 0 Comments

Yash Meshram
on 24 Oct 2019

i = input('Marks of the student: ');

if 0<=i && i<=59

fprintf('F grade\n');

end

if 60<=i && i<=69

fprintf('D grade\n');

end

if 70<=i && i<=79

fprintf('C grade\n');

end

if 80<=i && i<=89

fprintf('B grade\n');

end

if 90<=i && i<=100

fprintf('A grade\n');

end

##### 0 Comments

Vivek Sharma
on 8 Jun 2021

Please help me with the MATLAB code for the following problem. PDF is attached herewith.

Thank you.

##### 1 Comment

mahmood
on 17 May 2023

Edited: DGM
on 18 May 2023

clc;

clear;

% Constants

c = 13.03;

p = 19.93;

% Initial temperatures

T1 = 576;

T2 = 439;

% Number of impacts

m = 5;

% Initialize variables

T = (T1 + T2) / 2;

E = zeros(m, 1);

% Perform m impacts

for i = 1:m

E(i) = (c * p * T) / 23.5;

T = (T1 + T) / 2;

end

% Display the values of E for each impact

disp('Values of E for each impact:');

disp(E);

nejib
on 21 Aug 2023

>> t = 0:1/1e3:10;

d = [0:2:60;sin(1*pi*0.1*(0:2:60))]';

x = @rectpuls;

y = pulstran(t,d,x);

plot(t,y)

hold off

xlabel('Time (s)')

ylabel('Waveform')

>>

??? >>

##### 0 Comments

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