I want to add data points to the scatter plot that are not part of the data
ie. add points to find their concentration on a standard curve.

Steps to add data points to a scatter plot with a trend line in Microsoft Excel:

1. Create your scatter plot with the existing data points. To do this, select the data you want to plot, including the x-axis and y-axis values. Then, go to the "Insert" tab and select "Scatter" from the chart options.
2. Add a trend line by right-clicking on any data point and selecting "Add Trendline" from the drop-down menu.
3. In the "Format Trendline" pane that appears on the right side of the screen, select the "Options" tab. Under "Forecast," you can choose how far into the future you want the trend line to extend.
4. Add your new data points to the scatter plot by entering them into the worksheet as additional rows of data. Make sure to include both the x-axis and y-axis values for each point.
5. Once you have entered your new data points, they should automatically appear on the scatter plot. If they don't, you may need to adjust the axis scales to make sure they are visible.

You can add another series to the graph. While editing the graph,

Select Chart - Source Data - Series
Select ADD under the series window and enter the name and the X and Y values
for the series.

There are other ways to do this, as well.


"Samantha" wrote in message
...
I want to add data points to the scatter plot that are not part of the data
ie. add points to find their concentration on a standard curve.

The intent of your question is not entirely clear, as evidenced by
different interpretations by different responders.

If you click on the the plotted data series, the formula bar will
display the range of data plotted. If you extend that range in the
formula bar, you can add support x-values to visually extrapolate the
trendline beyond the data. Note however that when the mouse cursor
floats over the graph, y-values will be displayed only for actual x-y
data points in the graph, not for interpolated/extrapolated points on
the trendline.

If you right click on the trendline, and select Format Trendline, you
can go to the Options tab and request that the equation be displayed.
If you format that equation to display in scientific notation with 14
decimal places (to ensure that coefficient values are not obscured
through rounding) then you can calculate y-values for any x-values that
you desire. Alternately, most trendlies can be recalculated using
LINEST or LOGEST.

Jerry

Samantha wrote:

I want to add data points to the scatter plot that are not part of the data
ie. add points to find their concentration on a standard curve.