Exam 2: Review

Question 1

Determine the best fit cubic function through ordered pairs (y,z); display the constant term of the function

Answer 1

[p, s] = polyfit(y,z,3)

disp(p(4))

Question 2

Create a Cartesian plot of ordered pairs (x,y) in the upper right quadrant of figure number 66.

Answer 2

figure(66)
subplot(2,2,2)
plot(x,y)

Question 3

Place a message on the plot at coordinates (5,10) that displays the value of a numeric array, CLmax

Answer 3

text(5,10, num2str(CLmax))

Question 4

loglog(g,d,’–gd’)

Answer 4

plot of d as a function of g, both axis logarithmically, scaled dashed green line with green diamond data markers

Question 5

data = data(find(data~=0))

Answer 5

removes zeros from the data array

Question 6

z = uiputfile(‘*.bmp’,’Save data’)

Answer 6

z is the user selected location to save .bmp image. A command window will appear and allows the user to select where they wish to save the .bmp file

Question 7

set(gca,’YDir’, ‘Reverse’)

Answer 7

gca = get current axis

reverse direction of the y axis for the current set of axes

Question 8

command that would plot data in teh straightest alignment and include a dotted red line with res squares.

Answer 8

semilogy(x,y,’:rs’)

Question 9

List the three basic construsts of “structured programming” common to all programming languages

Answer 9

1. sequential
2. conditional
3. iterative

Question 10

When do you use a for loop?

Answer 10

Use a for loop when you know how many cycles the loop will need to complete, but not the final result.

Question 11

When do you use a while loop?

Answer 11

when you know the final condition but not how many cycles it will take.

Question 12

What is the difference between curvefit and spline?

Answer 12

Spine goes through every data point,

Curvefit does not

Question 13

List four basic mathematical functions we used for modeling data

Answer 13

1. exponential
2. Logarithmic
3. Linear
4. Power

Question 14

What is the forward difference?

Answer 14

(y_i+1 - y_i)/(x_i+1 - x_i)

Question 15

What is the backward difference?

Answer 15

(y_i - y_i-1)/(x_i - x_i-1)

Question 16

What is the central difference?

Answer 16

(y_i+1 - y_i-1)/(x_i+1 - x_i-1)

Question 17

What does it mean for a numerical method to be O(h^2)?

Answer 17

absolute error is proportionate to h^2 so if we have h the error drops to (1/2)^2 = 1/4

Question 18

What is the criterion that makes a generalized curvefit equation a “best fit” model for the data?

Answer 18

for a best curve fit model, the R^2 value needs to be closest to 1 as possibl;e

Question 19

Explain the criteria for using a for loop and a while loop?

Answer 19

"for" = known number of iterations, unconditional
"while" = conditional, unknown number of iterations, performs expression until the logical expression is false

Question 20

Explain the effects numerical integration and differentiation have on the propagation of uncertainty in data.

Answer 20

integration - attenuates uncertainty (lowers)

differentiation - increases uncertainty (amplifies)

Question 21

Determine the definite integral of a function where the array f contains values of the dependent variable and hte array t contains values of hte independent variable

Answer 21

p = trapz(t,f)

Question 22

Determine the derivative dp of a polynomial where the array p contains the coefficients of the polynomial arranged in descending powers

Answer 22

dp = polyder(p)

Question 23

Assume that a plot already exists in the current figure window and its aces are in polar coordinates To this plot, add another data series of the variables theta and r and plot it with red circles and a dashed line

Answer 23

hold on

polar(theta,r,’–or’)

Question 24

Plot hte variable principal as a function of the variable time on a plot with linear scaling on the x axis and logarithmic scaling on the y axis. Locate this plot in the lower right hand quadrant of the figure window

Answer 24

subplot(2,2,4)

semilogy(time,principal)

Question 25

Use teh cursor to paste a comment on the current figure that displays the value of hte variable earnings. Indicate in this comment that earnings is calculated at year’s end and that the units are in dollars.

Answer 25

comment=[‘year end earnings,’ num2str(earnings)]

gtext(comment)