Generating non linear chart

Generating non linear chart

Postby Guest » Fri Mar 01, 2019 7:11 am

Hi,
I recently suffered an acute kidney injury due to an infection. I’m trying to calculate the likely rate of healing (out of curiosity really I know only results will tell)

The first two readings from hospital in Feb were:

21st 34%
24th 48%

Assuming a linear progression I calculated that on the 28th it would be 57.32, in fact it was 56. So it seems the rate of healing is reducing.

My next test is on the 4th March. How do I create a chart to estimate the likely healing rate?
Guest
 

Re: Generating non linear chart

Postby Guest » Tue May 14, 2019 7:36 am

Yes, "two points determine a line" so there exist a unique line passing through two given data points. With three points there exist a unique quadratic (second degree) function. There are several ways to determine that function.

The simplest concept is this: A quadratic function can be written [tex]y= ax^2+ bx+ c[/tex]. If you are given the data points [tex](x_1,y_1)[/tex], [tex](x_2, y_2)[/tex], and [tex](x_3, y_3)[/tex], then putting those into that general equation, a, b, and c must satisfy [tex]y_1= ax_1^2+ bx_1+ c[/tex], [tex]y_2= ax_2^2+ bx_2+ c[/tex], and [tex]y_3= ax_3^2+ bx_3+ c[/tex]. Solve those three linear equations for a, b, and c.

In general, given "n" data points you can solve for "n" coefficients so get an "n-1" degree polynomial.
Guest
 


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