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Results tagged with curve-fitting
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user 35584
Methods used to fit curves (as in linear or non-linear regression) to data.
0
votes
R-Squared for a non linear curve
I calculate R-squared (R2) as "R2 = 1.0 - (regression_error_variance / dependent_data_variance)" and use it to tell me the fraction of the dependent data variance that is explained by the regression m …
- 1,216
3
votes
Accepted
Fitting curve to non-decreasing data
My equation search found that an inverse Harris yield density model:
y = x / (a + b*pow(x, c))
with fitted parameters of
a = 1.9953497744180733E+00
b = 4.6314864228655921E-03
c = 1.38778579616 …
- 1,216
3
votes
Accepted
Friendly alternative to sums of exponentials?
Thank you for posting the data. I found that several different sigmoidal equations each gave a good fit to the data. As one example here is the Weibull sigmoidal equation:
y = a - b * exp(-c * pow(x, …
- 1,216
0
votes
Is there a particular recommendation of exponent to use on the cost function when trying to ...
On my curve and surface fitting web site I have the following options for cost functions, each has a different fitting goal. For example, fitting to the lowest relative error squared means that a 5% e …
- 1,216
0
votes
Better way to fit/model data with high & low density areas (and with a geometric fit?)
One possibility is using wave height as a fitting variable and fitting the data to a 3D surface, as in:
z = f(x,y)
so that there is no need for grouping. If you are unfamiliar with surface fitting, …
- 1,216
0
votes
Best exponential decay line greater than 95% of data
If you add to the equation a constant value of, say, 25.0 then the existing parameter named "up_shift" will be adjusted by the nonlinear fitting algorithm to account for the added value. When using t …
- 1,216
1
vote
Double exponential fit in R
I also tried fitting the data you posted to a double exponential equation with similar results.
If you might use a different equation, I was able to fit the data you posted to the Extreme Value peak …
- 1,216
4
votes
Accepted
Which kind(s) of curves should I use to fit these data?
I found a simple 3D equation which seems to fit the data OK, see the fit statistics and plots below:
RESPONSE = a * pow(COV1,b) * pow(COV2,c) + Offset
Fitting target of lowest sum of squared absolut …
- 1,216
5
votes
Accepted
Curve fitting when data has a sharp initial slope and then tapers off
My equation search on your data turned up a simple two-parameter power equation, "y = a * pow(x, b)", with parameters a = 1.0769014059561925E+00 and b = 1.4153886539395866E-01 yielding R-squared = 0.7 …
- 1,216
2
votes
Accepted
Simultaneously curve fitting for 2 models with shared parameters in R
Per my comment, here is working Python code that fits two data sets to two straight lines with different slopes and a single shared offset parameter. This is not intended as a direct answer, but is he …
- 1,216
2
votes
How to fit a set of curves having some free and some shared parameters?
One possibility that should scale well is to: A) Independently fit each data set, then B) Determine the mean (or median) value of the independently fitted values for what should be the shared paramete …
- 1,216
0
votes
Accepted
chi-squared of simultaneous (least-squares) fitted data
One approach would be to calculate the six individual values, one for each data set, and then sum the relative contribution to the total based on the number of data points in each data set.
As an exa …
- 1,216
0
votes
(How) Can I fit a dataset with some parameters fit globally?
One approach is to construct the fitting function like so:
if (data in dataset 1):
bottom+(top-bottom)/(1+10**((logIC50_1-x)*HillSlope_1)) # "_1"
elif (data in dataset 2):
bottom+(top-bottom) …
- 1,216
0
votes
Interpreting total square error when function values are of many orders of magnitude
You might consider comparing this fit, made to the lowest sum of squared absolute error, to one made with a different fitting target such as the lowest sum of squared relative error. There are times w …
- 1,216
2
votes
Multi-variable nonlinear scipy curve_fit
Here is a 3D surface fitter using your equation and my test data that makes a 3D scatter plot, a 3D surface plot, and a contour plot. You should be able to click-drag the 3D plots with the mouse and r …
- 1,216