## Sunday, January 30, 2011

### Correlation analysis

# correlation analysis tool
n=7
decimal(3)
font "arial",10,100
graphsize 500,500
dim x(n) : dim y(n)
tx=0 : ty=0
x = {2,3,3,4,4,6,5}
y = {1,2,4,5,4,8,7}
for m = 0 to n-1
tx=tx+x[m] : ty=ty+y[m]
next m
meanx=tx/n : meany=ty/n
sdx=0 : sdy=0: sdxy=0
for m = 0 to n-1
sdx=sdx +(x[m]-meanx)^2
sdy=sdy +(y[m]-meany)^2
sdxy=sdxy +(x[m]-meanx)*(y[m]-meany)
next m
sx=(sdx/n)^.5
sy=(sdy/n)^.5
covxy=sdxy/n
r= covxy/(sx*sy)
m= covxy/sx^2
c= meany-m*meanx
# Standard deviation covariance correlation coefficient and line of best fit
Print "Sx="+sx
Print "Sy="+sy
Print "Sxy="+covxy
print "r="+r
print "y="+m+"x+"+c
# graph parameters
minx=-10 : maxx=10 : miny=-10 : maxy=40
rangex=(maxx-minx)
rangey=(maxy-miny)
for i= 0 to 10
line 0,i*50,500,i*50
line i*50,0,i*50,500
text i*50,480,minx+rangex*i/10
text 0,500-i*50,miny+rangey*i/10
next i
color red
for i= 0 to n-1
circle (x[i]-minx)*(500/rangex),500-(y[i]-miny)*(500/rangey),5
next i
color blue
for i= 0 to 500
circle i,500*(1+(-c+miny)/rangey)-m*(rangex/rangey)*(i+500*minx/rangex) ,2
next i