Linear trendline to forecast data

[tjaques]

I have a simple chart showing calls by day average.
Year
1990=100
1995=200
2010=400
2014=515

I want to create a simple line graph and add a trendline showing what calls might be in 2025. Help please. I think I'm over thinking this!

 

[thisoldman]

This is simple and quick. It may be all you need.

<tbody>
[TD="class: xl64"]Year[/TD]
[TD="class: xl64, width: 64"]Calls[/TD]

[TD="class: xl64, align: right"]1990[/TD]
[TD="class: xl64, align: right"]100[/TD]

[TD="class: xl64, align: right"]1995[/TD]
[TD="class: xl64, align: right"]200[/TD]

[TD="class: xl64, align: right"]2010[/TD]
[TD="class: xl64, align: right"]400[/TD]

[TD="class: xl64, align: right"]2014[/TD]
[TD="class: xl64, align: right"]515[/TD]

[TD="class: xl64, align: right"]2025[/TD]
[TD="class: xl64, align: center"]#N/A[/TD]

</tbody>

Select the entire block and insert a scatter(xy) chart. Then add your trendline.

A line chart would distort the horizontal scale, an xy-chart gives a properly spaced scale.
Excel won't plot the #N/A value in an xy-chart.
You have to include x-values up to or beyond the last point to be displayed on the chart. So you have to include the year 2025.