[ncl-talk] Regarding RegLine (coefficient of determination)

Barry Lynn barry.h.lynn at gmail.com
Tue Oct 3 08:10:53 MDT 2017

```Hi:

I didn't see that this function has been updated to calculate the
coefficient of determination (r).

I did see this e-mail and one after (e.g.:
https://www.ncl.ucar.edu/Support/talk_archives/2009/2202.html

but this (below) may be more useful for users wanting the simplest approach
to calculating statistics for a line.

begin

x = (/1,2,3,4,5,6,7,8,9,10/)

y = (/0.6,1.6,1.2,2.2,2.3,3.1,2.8,4.1,4.7,3.3/)

rc = regline(x,y)  ; function as is.

print("rc = " + rc)

printVarSummary(rc)

sum_xy = sum(x*y)

sum_x = sum(x)

sum_x2 = sum(x^2)

sum_y = sum(y)

sum_y2 = sum(y^2)

n = dimsizes(x)

r_n = n*sum_xy - sum_x*sum_y

r_d =(n*sum_x2  - (sum_x)^2)*(n*sum_y2  - (sum_y)^2)

r = r_n/sqrt(r_d)

print(r)

r2 = r^2

print(r2)

end

Answer r = 0.9075 and r2 = 0.82364.

--
Barry H. Lynn, Ph.D
Senior Lecturer,
The Institute of the Earth Science,
The Hebrew University of Jerusalem,
Givat Ram, Jerusalem 91904, Israel
Tel: 972 547 231 170
Fax: (972)-25662581

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