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CS 121 – Quiz 2

CS 121 – Quiz 2. 2010 Feb 1 st. Question 3 Script Outlines. #it is always beneficial to write “restart” at the beginning of your script to clear all variables restart: #Use a, b, g, d to represent alpha, beta, gamma, and delta, which are constants in the formula

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CS 121 – Quiz 2

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  1. CS 121 – Quiz 2 2010 Feb 1st

  2. Question 3 Script Outlines • #it is always beneficial to write “restart” at the beginning of your script to clear all variables • restart: • #Use a, b, g, d to represent alpha, beta, gamma, and delta, which are constants in the formula • a:=0.04; b:=5E-4; g:= 0.2; d:=5E-5; • Cc

  3. Question 3 • #Initial rabbit and fox population • r0:=5486; f0:=15; • #Set a variable “years” to represent the number of years that the model should run, which is also the number of loop • years:=45;

  4. Question3 • #Write a for loop • for i from 1 to years do • #calculate the population in next year next_r := r + floor(r*(a-b*f)); next_f := f – floor(f*(g-d*r)); • #update the rabit and fox population r:=next_r; f:=next_f; • end do; • #print out the population at the end of loop

  5. Question 4 • You might see different graphs in question4, but you can solve it the same way. • You are given a bunch of functions: • g := (t,c) -> plots[display](plottools[line]([t, 0], [t, t+1], color=c)); • gb := (t,c) -> plots[display](plottools[line]([0,t], [t, t+2], color=c)); • f1 := (t,c) -> plots[display](plottools[disk]([t+1,1], color = c)); • ga := (t,c) -> plots[display](plottools[disk]([t+3,1], color = c)); • s := (a,b) -> plots[display]([a(1,red),b(2,blue)], scaling=constrained); • f := (a,b) ->plots[display]([b(-5,red), a(-3,blue)], scaling=constrained);

  6. Question 4 • And also a graph

  7. Question 4 • In order to plot the target graph, you need a red disk and a blue disk first. • #Notice function f1 and ga are perfect to do it. • #Observe where the center of the circle is and the color of the disk • #pass appropriate values to function f1 and ga • f1(1,red) • ga(2,blue)

  8. Question 4 • Then we need to display two disks in the same graph • #Notice function s is to combine 3 graph a and b together • #a takes 2 parameter: 1 and red • #b takes 2 parameters: 2 and blue • #those are the values we plugged in f1 and ga • #so a and b can be substituted by f1 and ga • Finally we came up with the solution • s(f1,ga)

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