Excel: Can I force a linear trendline through the origin?

  • Thread starter Thread starter Guest
  • Start date Start date
Yes, open at the Option tab when you make (or format) a trendline
There is a text box to set intercept to any value (including 0)
best wishes
 
I have done that, but it is not working. Perhaps it is because I am plotting
a log-log graph and therefore there is no actual zero value for the y-axis.
But I need the line to pass through the origin, and because the data covers
several decades, it needs to be plotted as log-log. Any ideas?

Bill
 
Try this it may work
1) Display the equation of the line.
2) use the equation to calculate the value y by taking x as 0.0000001 or any
value
3) add these values (x,y) to your series as new points

you can then hide the marker if you want.


Hope this helps
 
Hi,

If the plot 'looks' linear in the log-log plot, then the x,y-data are NOT
linear (and y =a* x^m). calculate the logarithms of the x and y values in
new columns and make a plot of log y vs log x, and get a trendline (which you
can force to pass through the origin; i.e., you are forcing "a" to be equal
to 1). However, note that the slope of this line is indeed the exponent "m"
in the equation, y = x^m.

Formatting the axes of a graph to logarithmic scales only changes the visual
appearance of the graph, but does not actually transform the x,y-data to
their logarithm values. If you still want to stick to the y vs x plot with
log-log scales(and not the log y vs log x plot), you can still get a
trendline that 'looks' linear by selecing "Power" and not "linear" for the
trendline type. The trendline equation will show up as y = a*x^m; but you
can't force "a" to become equal to 1. The latter can be done using Excel's
'Solver' utility.

Regards,
B. R. Ramachandran
 
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