MATLAB POLYSPACE RELEASE NOTES Manual de usuario descargar pdf (Pagina 186)

5 Data Analysis

of the variables to normalize values between +1 and –1. The results are

correlation coefficients, computed by the MATLAB

corrcoef function:

R12 = corrcoef([c1 c2])

R12 =

1.0000 0.9331

0.9331 1.0000

r12 = R12(1,2) % Correlation coefficient

r12 =

0.9331

r12sq = r12^2 % Coeffi cient of determination

r12sq =

0.8707

Because it is normalized, the value of the correlation coefficient is readily

comparable to values for other pairs of intersections. Its square, the coefficient

of determination, is the variance about the least-squares line divided by the

variance about the m ean. That is, it is the proportion of variation in the

response (in this case, the traffic volume at intersection 2) that is eliminated

or non-causally “explained” by a least-squares line through the scatter.

3-D Scatter Plots

A 3 -D scatter plot, created with the MATLAB scatter3 function, shows the

relationship between the traffic volume at all three intersections:

figure

scatter3(c1,c2,c3,'filled')

xlabel('Intersection 1')

ylabel('Intersection 2')

zlabel('Intersection 3')

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MATLAB POLYSPACE RELEASE NOTES Manual de usuario Pagina 186