Plotting & Logical Indexing
How many data points do you want for curve fitting?
50
(What are those symbols and what do they do?)
|
&
The or symbol for when any true comparison will return true.
The and symbol for when all of the comparisons need to be true to return true.
What is different about exporting data to a .txt file in MATLAB and importing data from a .txt file in MATLAB
Importing: fscanf and 'r'
Exporting: fprintf and 'w'
BOTH: use fopen and fclose
How many "end"s does this code need?
while
for
if
elseif
else
if
for
if
function
while
for
9
Write the basic outline of a function with 3 inputs and 2 outputs
AND call your function
[OutName,OutName] = Name(a,b,c)
function [Out1,Out2]=Name(In1,In2,In3)
Commands or whatevs
end
What is logical indexing?
Using a logical array (a matrix of logical 0s and 1s) as an index to extract certain values
E=[0 1 3 4]
F=[1 1 3 4]
Multiply E by F
G=E.*F
Which is true?
1) numel() and length() give you the same result for a vector
2) numel() and length() give you different results for matrices
3) numel() and length() give you different results for vectors
4) numel() and length() give you the same results for matrices
1 & 2
numel() gives the same result for vectors and different results for matrices
How many times will this loop run?
for idx=1:4
for idy=1:3
for idz=1:2
fprintf('Camp Rock!\n')
end
end
end
4*3*2=24
What dou you include in the comments for your function?
Format of the call, description of inputs and outputs, description of commands
Format of polyfit(), polyval(), and plot()
Coefficients = polyfit(x,y,order)
New_Y=polyval(Coefficients, x)
plot(x,New_Y)
Are these valid or not?
3<A<8
A>3 & A<2
A>3 | A<2
NO
NO
YES
Where must files be on your computer in order for MATLAB to open them?
Where do they show up on MATLAB?
They must be in the correct file path open on MATLAB
They generally show up on the top left of your screen in the "Files" window. You can also click on them to open them in your script area.
Fix this code (STILL USING A WHILE LOOP):
while idx=1:3
fprintf('I like %i\n',idx)
end
idx=1;
while idx<=3
fprintf('I like %i\n',idx)
idx=idx+1;
end
Create and call a function that finds the average of an inputted set of data (NOT USING THE mean command)
Comments not necessary
B=FindAvg(A)
function Avg=FindAvg(Vec)
Avg=sum(Vec)/length(Vec);
end
Given a vector B use logical indexing to create a new vector C which has the B values that are not equal to the mode and are less than the mean
C=B(B~=mode(B) & B<mean(B))
BONUS!!
What is my (Halle's) favorite band??
Queen or Abba
FavChristmasMovie=Die Hard
Is FavChristmasMovie a string or character array based on the following output:
strlength(FavChristmasMovie) = 8
length(FavChristmasMovie) = 8
size(FavChristmasMovie) = 1 8
Character array
Given a vector F
Write code that will determine how many numbers are equal to 4, less than four, and greater than four
Fours=0;
Big=0;
Lil=0;
for idx=1:length(F)
if F(idx)==4
Fours=Fours+1;
elseif F(idx)>4
Big=Big+1;
elseif F(idx)<4
Lil=Lil+1;
end
end
Create a useful function that has no output or input
Bunch of possibilities:
function ccc
clc
close all
clear
end
Make a graph of vectors X and Y which adheres to ENGR 130 style guidelines and plots BOTH the individual points and a curve fit in different colors. (The equation of Y is Y=-X^3+2x^2)
X=[1:5];
Y=-X.^3+2.*X.^2;
Coeff=polyfit(X,Y,3);
Big_X=linspace(X(1),X(end),50);
New_Y=polyval(Coeff,Big_X);
hold on
plot(X,Y,'*r','LineWidth',3)
plot(Big_X, New_Y,'--b','LineWidth',3)
hold off
title('Cool title')
xlabel('X label (units)')
ylabel('Y label (units)')
legend('Points','Fit')
Given a vector of unknown (even length) create a matrix with the first half of the vector in row 1 and the second half of the vector in row two
B(1,:)=[A(1):A(length(A)/2)]
B(2,:)=[A(length(A)/2+1):A(length(A))]
The four commands used with .txt files AND their inputs
ID=fopen('FileName.txt','r/w')
fprintf(ID,'Hey %i',VarName)
fscanf(ID,'%i', #)
fclose(ID)
Create code for a game that allows a user to input a letter and if they enter a b they win and if they enter anything else they try again.
Gus='w';
while Gus~='B' & Gus~='b'
Gus=input('Guess a letter:\n','s');
if Gus == 'B' | Gus=='b'
fprintf('You won!\n')
break
else
fprintf('Try again :(\n')
end
end
Create and call a function that outputs the volume and surface area of a rectangular prism given the dimensions
[Vol, SA]=Calcs(1,2,3)
function [Volume,SurfArea]=Calcs(a,b,c)
Volume=a.*b.*c;
SurfArea=2*(a.*b)+2*(b.*c)+2*(c.*a);
end