The data at both ends of the plot tracks the fitted curve. The confidence bounds are closer together indicating that there is less uncertainty in prediction. This graph shows a much better fit to the data. Then, drag the vertical reference line to the x-value of 2 (or type 2 in the X Values text box). In the Degree box at the top, type 3 for a cubic model. The two points to the right are dragging down the estimate of the slope.
#Polytool find epsilon with error how to
The bulk of the data with x-values between zero and two has a steeper slope than the fitted line. I also know that what I'm trying to show is equivalent to finding an alternating set for the function of at least two points, but I don't know how to combine this idea with the information given. If you do not specify the degree of the polynomial, polytool does a linear fit to the data. The variables x1 and y1 are data points from the "true" function without error. The variables x and y are observations made with error from a cubic polynomial. To start the demonstration, you must first load the data set. You can use polytool to do curve fitting and prediction for any set of x-y data, but, for the sake of demonstration, the Statistics Toolbox provides a data set ( polydata.mat) to teach some basic concepts.
An Export list box to store fit results into variables.A Close button to end the demonstration.Bounds and Method menus to control the confidence bounds and choose between least squares or robust fitting.A draggable vertical reference line to do interactive evaluation of the polynomial at varying x-values.A data entry box to evaluate the polynomial at a specific x-value. The polytool demo is an interactive graphic environment for polynomial curve fitting and prediction.A data entry box to change the degree of the polynomial fit.y-axis text to display the predicted y-value and its uncertainty at the current x-value.
The polytool demo is an interactive graphic environment for polynomial curve fitting and prediction. Demos (Statistics Toolbox) Statistics Toolbox
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