Question

Hi,

I have the following formula:

UEF=0.8165+0.2254tan^-1((Year-1967.5)/21.25)

Which is supposed to produce the following values of UEF:
UEF=1.06 for year = 2010
UEF=1.03 for year = 2000
UEF=1.00 for year = 1990
UEF=0.94 for year = 1980
UEF=0.85 for year = 1970
UEF=0.74 for year = 1960
(note that the above UEF values may not be quite right as I have taken them from a plot which was pretty low quality).

The problem is that when plugging various values for the variable "Year" into the formula, I am unable to replicate the above quoted UEF values that I took from the plotted graph of the relationship. I recieve the following answers which are obviously well out:

UEF=15.11 for year = 2010
UEF=13.62 for year = 2000
UEF=11.33 for year = 1990
UEF=7.68 for year = 1980
UEF=2.33 for year = 1970
UEF=-3.57 for year = 1960

I would be most gratful if anyone could offer an insight as to where I'm going wrong.

Best regards
Aaron