Trend formula query

[mtait]

Hi - can anyone explain how the (c) number is calculated for the trend line - my data is (for example):

86.96
99.12
85.48

The trend formula is y=0.74x+92

I can't see at all where the 92 is derived from?

Thanks, Mark

[shg]

Welcome to the forum.

Trend is a linear regression. Where's the rest of the data?

[mtait]

Thank you.

The full data is:

Date GOS
01/11/2008 86.96
02/11/2008 99.12
03/11/2008 85.48
04/11/2008 87.84
05/11/2008 91.29

That is all the data I was looking at - I wanted to predict what the GOS would be on 7th November 2008

I want to be able to predict the linear trend (with more data when I have it) further into the future too - but the (c) part of the equation, I took to be the point where the trend line crossed the axis - which I would have thought would have been the first value - ie. 86.96 - which is why I'm confused about where the 92 comes into the formula?

Thanks for any help,

Mark

[shg]

When you do TREND(y, ,newx), you get a linear fit with x values as categories = {1,2,3, ...}. So 92 is the y intercept, which is, by definition, for x = 0.

If you do TREND(y, x, newx), it does the regression against the actual x values, and you'll get a (very) different intercept.