[ncl-talk] Linear equation for regline_state
mark vogel
mdvogelii at gmail.com
Mon May 2 10:50:10 MDT 2016
Dear NCL talk
How can I put the equation for the linear regression?
As my graph I got the y = 1.87x - 0.6 it does not seem right to me when x =
0 and y = -0.6
It does not seem right to me when x = 0 y is -0.6 but I follow the
reline_stats equation as in the ncl link
http://www.ncl.ucar.edu/Document/Functions/Contributed/regline_stats.shtml
My code is
; calculate the regression coefficient (slope)
;************************************************
rc1 = regline_stats(x, y2) ; slope
rc1 at units = "(W/m2)"
rc2 = regline_stats(x, y3) ; slope
rc2 at units = "(W/m2)"
rc3 = regline_stats(x, y4) ; slope
rc3 at units = "(W/m2)"
;************************************************
; create an array to hold both the original data
; and the calculated regression line
; ---------
; y = mx+b
; m is the slope: rc returned from regline
; b is the y intercept: rc at yave attribute of rc returned from regline
;************************************************
pltarry = new ((/2,2191/),float)
pltarry(0,:) = y2 ; use markers
pltarry(1,:) = rc1*(x-rc1 at xave) + rc1 at yave ; use solid line
pltarry1 = new ((/2,2191/),float)
pltarry1(0,:) = y3 ; use markers
pltarry1(1,:) = rc2*(x-rc2 at xave) + rc2 at yave ; use solid line
pltarry2 = new ((/2,2191/),float)
pltarry2(0,:) = y4 ; use markers
pltarry2(1,:) = rc3*(x-rc3 at xave) + rc3 at yave ; use solid line
x1 = ispan(-100,500,1)
y = x1
labels1 = "y=" + sprintf("%4.2f",rc1 at b(1)) + "x+" + sprintf("%4.2f",rc1 at b
(0))
labels2 = "y=" + sprintf("%4.2f",rc2 at b(1)) + "x" + sprintf("%4.2f",rc2 at b(0))
labels3 = "y=" + sprintf("%4.2f",rc3 at b(1)) + "x+" + sprintf("%4.2f",rc3 at b
(0))
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