MONT 102N -- Environmental Mathematics 

The Correlation Coefficient and Its Geometric Meaning
October 17, 2011
 

 

Given a scatter plot, the correlation coefficient  r 

is a way to quantify how close the points (x, y) are to 

lying along a single straight line.  The coefficient
takes values in the range  -1to 1:
 



A value of r = -1:  indicates that the points all
                             lie along a line of negative slope

                 
r = 0:    indicates no linear relationship at all

                 
r = +1:  indicates that the points all
                              lie along a line of positive slope

Values between 0 and 1 or between -1 and 0  indicate
 

the ``strength'' of the tendency toward a linear relation
between  
x  and  y.  Here are some illustrative examples:     

 

Computations 

 

CloudPlot(5, 11, .9); 1 

 

Correlation coefficient is r =
Plot_2d
 

CloudPlot(5, 11, .7); 1 

 

Correlation coefficient is r =
Plot_2d
 

CloudPlot(5, 11, .5); 1 

 

Correlation coefficient is r =
Plot_2d
 

CloudPlot(5, 11, .3); 1 

 

Correlation coefficient is r =
Plot_2d
 

CloudPlot(5, 11, .1); 1 

 

Correlation coefficient is r =
Plot_2d
 

CloudPlot(5, 11, -.1); 1 

 

Correlation coefficient is r =
Plot_2d
 

CloudPlot(5, 11, -.3); 1 

 

Correlation coefficient is r =
Plot_2d
 

CloudPlot(5, 11, -.5); 1 

 

Correlation coefficient is r =
Plot_2d
 

CloudPlot(5, 11, -4); 1 

 

Correlation coefficient is r =
Plot_2d