Trend lines

[Arthur]

I'm trying to use the LINEST function. Apparently it
requires that formulas be entered in an array. The online
help has the following example:

Cells C5, D5, and E5 contain values.
Use the formula =TREND(C5:E5,,{4,5}) to project the fourth
and fifth values in the monthly sequence based on the
first three values.

All I get is a circular reference or a zero when I try
this. Do you use shift-ctrl-enter to enter the Trend
formula? Does the same formula get entered in cells F5 AND
G5?

I got to the help screen I'm looking at through LINEST,
and then selecting "For more information about array
formulas, click __" which is contained in the LINEST help
subject.

Thanks,
Art

 

[Jerry W. Lewis]

If you do not array enter the formula, you will only get the straight
line extrapolation to x=4. If you select two columns and array enter
the formula, you should get the extrapolation to x=4 and x=5.

Jerry

 

[Arthur]

Jerry, your suggestion worked. Thanks. Care to help me
understand what the numbers represent?

Cells C5, D5, and E5 contain 200, 300, 100.
Selected cells F5 and G5 and array entered the formula
=TREND(C5:E5,,{4,5})
The formula returns 100 in cell F5 and 50 in G5.

Art

 

[Jerry W. Lewis]

You fit a straight line to
x y
1 200
2 300
3 100
and got an estimated line y = 300 - 50*x, which does not fit your data
very well (R^2=0.25). You then asked what the value of that trendline
was for x=4 and x=5 and got the answers 100 and 50.

Jerry