Question

Please write the codes in MATLAB.

HW8_4 Fit the data in the table using linear regression. Plot the data points as well as the regression line. Determine the value of y whenx = 7.2 and print it to the screen using fprintf Then repeat the process, regressing in the opposite way (x vs y) to find the equation of the line needed to determine the value of x when y is 15 Optional brain food: Do you get the same line & same r? Answer in comments. 6 7 89 10 26.7 20.2 16.8 15.3 15.1 9.35.1 2.8-1.1-8.4 HW8_5 Fit the recorded daily temperatures in Lubbock, TX on September 15, 2015 to the two periodic models Plot each of the curves on a separate graph. Include the data points, and place the equation (with correct coefficients) in the title; and r value on the plot using the text command Time of day 12 mid2 am4 am6 am 8 am 10 am Noon 2 pm4pm6pm 8pm10pm 12 mid 10 12 14 16 18 2022 24 Temp (F) 77.0 73.972.0 68.0 64.0 72.082.088.090.0 91.0 84.9 80.175.9

Answer 1

%we are supposed to answer 1 question at a time

%HW8_4

clear
clc
close all
x=1:10;
y=[26.7 20.2 16.8 15.3 15.1 9.3 5.1 2.8 -1.1 -8.4];
%y=mx+c
p1=polyfit(x,y,1);
plot(x,y,'*',x,p1(1)*x+p1(2))
xlabel('x')
ylabel('y')
title(sprintf(' y = (%f) x + (%f)',p1))
legend('Data points','Linear fit')
sse=sum((y-polyval(p1,x)).^2);
ssto=sum((y-mean(y)).^2);
r21=1-sse/ssto;
fprintf(' y = (%f) x + (%f)\n',p1)
fprintf(' R squared value: %f\n',r21)
fprintf(' value of y when x = 7.2: %f\n',p1(1)*7.2+p1(2))
%x = ym + c

p2=polyfit(y,x,1);
figure
plot(y,x,'*',y,p2(1)*(y)+p2(2))
ylabel('x')
xlabel('y')
title(sprintf(' x = (%f) y + (%f)',p2))
legend('Data points','Linear fit')
sse=sum((x-polyval(p2,y)).^2);
ssto=sum((x-mean(x)).^2);
r22=1-sse/ssto;
fprintf(' x = (%f) y + (%f)\n',p2)
fprintf(' R squared value: %f\n',r22)
fprintf(' value of x when y = 15: %f\n',p2(1)*15+p2(2))

Command Window y-3.463030) x+(29.226667) R squared value: 0.968985 value of y when x = 7.2: 4.292848 x= (-0.279808) y + (8.348449) R squared value: 0.968985 value of x when y 15: 4.151324 Figure Figure 2 File Edit View Insert Tools Desktop Window Help File Edit View Insert Tools Desktop Window Help y (-3.463030) x+ (29.226667) x (-0.279808) y (8.348449) 12 Data points -Linear fit Data points Linear fit 25 10 20 15 10 ×6 10 10 15 20 25 30