standard curve

[Guest]

I am trying to plot data where I have an extablished standard curve, and I
would then like to plot my samples and extrapolate what their x value is
based on their known y value. Basically I would like to create a line or
curve with my first set of data, and then add individual points "on top" of
that curve. Can anyone help me with this?
Thank you,
Erica
(e-mail address removed)

 

[Jerry W. Lewis]

You can fit a line or polynomial to either the original or log
transformed data by adding a trendline to the chart. Coefficients can
be extracted directly from the chart using David Braden's code
http://groups.google.com/[email protected]
or can be computed with SLOPE() and INTERCEPT() for a straight line or
LINEST() for polynomials
http://www.stfx.ca/people/bliengme/ExcelTips/Polynomial.htm
For truly nonlinear models, such as a 4 or 5-parameter logistic, then
you can use solver to obtain the coefficients of the standard curve
http://groups.google.com/groups?selm=3DD65D20.9090304@no_e-mail.com
which can then be used to calculate fitted values for plotting the curve.

For plotting sample values, you must provide an x value as well as a y
value. If you want to plot the y-value on the curve, you can either
invert the curve (y=a+b*x implies that x=(y-a)/b) or consider the
various suggestions in
http://groups.google.com/groups?selm=40A04658.9000505@no_e-mail.com

Jerry