BME201

Final Exam

what is a scalar

single number

what is a character

letter or number

what is an array

multiple scalars

what is a string using ‘ ‘

character array

what is a string using “ “

string

what are the two requirements for variable names?

clear/descriptive, succinct

create a custom function heading

function[outputs] = FunName(inputs)

create an anonymous function

FunName = @(inputs) code

if an input needs to be a character/string what needs to be before the closing parenthesis

‘s’

what is fprintf %f

float

what is fprintf %i

integer

what is fprintf %c

character

what is fprintf %s

string

what is fprintf %e

scientific notation

what is \t for

indent(4 spaces)

what is \n for

new line

brute force defining rows for 1D array

[1 2 3 4];

brute force defining columns for 1D array

[1;2;3;4]; (or [1 2 3 4]’;)

colon operator for rows in 1D array

row = start:step size:stop

how does linspace work

row = linspace(start, stop, total elements)

index x to get all odd elements

x(1:2:end)

index x to get all even elements

x(2:2:end)

to multiply or divide scalar and vectors what is needed

.* or ./

what does the size function return

[rows, columns]

what does the length function return

longest dimension

what does numel return

number of elements

change the 3rd element of array x to 10

x(3) = 10;

what would be the output when x = [1 2 3] and then x(end + 2) = 5

[1 2 3 0 5];

how would you reverse the order of array x

x = x(end:1:-1); (or x = flip(x))

what does mod(a, b) return?

remainder of a/b

when and how does && work

only works with scalars and if 1 is false don’t evaluate 2

when to use for loops

number of reps is known

when to use while loops

number of reps is unknown but we have a stopping condition

how does a for loop start

for k = 1:length(x)

how does a while loop start

while condition true

write out euler method

yes

which direction do the rows count up in a 2D array

-y

which direction do the columns count up in a 2D array

+x

what does x(:, 2) produce in a 2D array

all rows, 2nd column

what does x(3, :) produce in a 2D array

3rd row, all columns

brute force create x, a 2D array with 123 as the top row and 456 as the bottom row

x = [1 2 3; 4 5 6];

store spreadsheet (FileName.ext) data into variable data

data = readmatrix(‘FileName.ext’)

create spreadsheet (named filenameNew.ext) using dataNew

writematrix(dataNew, ‘filenameNew.ext’)

create a text file (filename.dat) using fprintf

fid = fopen(‘filename.dat’, ‘w’)

fprintf(fid, ‘…’)

fclose(fid)

Create vector P using polyfit

P = polyfit(x, y, N)

What is the N in polyfit(x, y, N)

highest exponent in the polynomial

use sum function to sum along the columns of array x

[1 2 3]

sum(x, 1)

use sum function to sum along the rows of array x

[1

2]

sum(x, 2)

how does the max function work ** dim is either 1 for columns or 2 for rows

[max values, index/location] = max(data, [ ], dim)

how can you find the global max of x and store it in variable y

y = max(max(x));

take the average of x

mean(x)

store the standard deviation of x in the variable y *rms works the same way

y = std(x, dim)

create a scatter plot using plot

plot(x, y, ‘shape’)

create a scatter plot using scatter

scatter(x, y, marker size, ‘options’)

create a histogram with m sized bins

histogram(x, m)

create a box plot

boxplot(x)

create a bar graph with error bars

bar(x, y)

hold on

errorbar(x, y, error bar size, ‘options’)

hold off

how does machine learning work?

pattern recognition

how does fitctree work?

based on decision trees, binary choices

how does fitcnet work?

creates neural network, how your brain works, better for complicated systems

what does a confusion matrix show?

predictions and actual results in a grid

import image (img.ext) into variable img

img = imread(‘img.ext’)

display image (img)

imshow(img)

save image (imgNew) as filename.ext

imwrite(imgNew, ‘filename.ext’)

convert rgb image (img) to grayscale (imgGray)

imgGray = rgb2gray(img);

convert rgb image (img) to binary image (imgBin)

imgBin = im2bw(img, fraction)

crop image (img) and store in variable imgCrop

imgCrop = imcrop(img[xTopLeft, yTopLeft, xSize, ySize])

color thresholding for red from image (img)

red = img(:, :, 1)

color thresholding for green from image (img)

green = img(:, :, 2)

color thresholding for blue from image (img)

blue = img(:, :, 3)

info for diff functions

1D arrays, easy to do N derivatives, loses data points for each derivative

info for gradient function

2D arrays, harder to do N derivatives, handles nonconstant step sizes, may have weird endpoints

take the 2nd derivative of y using diff function

diff(y, 2)

take the first derivative of y using gradient, store in v with t as the spacing for dimensions

v = gradient(y, t)

take the integral using the trapezoid rule and store it in yInt

yInt = trapz(x, y) + initial value

how does a 3D plot function work

plot3(x, y, z, ‘options’)

how does the mesh function work for 3D plots

mesh(X, Y, Z), colors along grid, white between grid

how does the surf function work for 3D plots

surf(X, Y, Z), color between the grid, black grid lines

how does the colorbar function fit into the title label when making a graph

title(colorbar, ‘title’)

how does the quiver plot work?

quiver(X, Y, U, V, scale for vectors)

how does streamslice plot work?

streamslice(X, Y, U, V, number of streamlines)

what is the difference between quiver and streamslice plots?

quiver looks like a vector field, streamslice has the lines connected

what are the U and V in the streamslice and mesh functions?

x and y vector magnitudes