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Curve fitting equation & tracer software; pump curve and system curve plotting, intersection point of two curves, digitizing over existing graph image

Rethink, Reinvent . . . solve a task or two just-in-time

CurveFit Tracer - curve fitting software

> to obtain curve fitting equation from graph image/published graph

> to digitize graph

> to find complex intersection points of 2 curves (with visualisation on logarithmic scale)

> to plot pump curves (1 or 2 identical pumps in parallel/series) and system curve with intersection point

To take a glance at all pocketEngineer software and OS requirements, click Software List.

Curve Fit Tracer ... just point-and-click to get curve fitting equation

There are situations when you need to find a curve fit equation from the given graph image / published graph. Let's get stuff done in a simple yet effective way.

Trace Curve and Obtain Equation from given Graph Image

How do you find the equation of a curve from the graph?

For example, given the pump curves below, this app can trace the existing curve from the graph image/published graph, and obtain a curve fitting equation.

For linear-linear graph, curve fitting equations available are linear, parabolic and cubic to fifth order of polynomial equation.

Also available are power and exponential curve fitting.

For straight line on log-log graph plot, curve fitting equation is a power function.

You can copy & paste the equation for other purpose.

The program can be used as a simple graph digitizer too. Digitized X & Y data can be copied and pasted onto an Excel sheet for further processing.

For details, download these how-to documentations:

(1)Linear graph (2)Log-Log graph (3) Digitize log-log graph

Note: This app cannot do semi-log graph. For curve line on log-log graph, the program can digitize X & Y data for further processing.

Intersection Points

This app can find complex intersection points of 2 irregular lines as shown above.

You can key-in the points for the 2 lines, or generate points from equations.

The basic built-in equations to generate points are:

- linear line: y = c * x + k

- parabolic: y = b * x^2 + c * x + k

- cubic: y = a * x^3 + b * x^2 + c * x + k

- power: y = c * x^n

The comparison and validation results can be downloaded here.

Lines intersection point with visualisation on logarithmic scale

Line 1: y = x^1.85; Line 2: y = x^2

Numerical Method: Line-Polynomial equation intersection points

see downloadable intersections example in applied pyschrometric

and Graphical Method

The following example shows the pump-system curves intersection point. The points are generated from the following equations:

Line 1 equation: Y = (12.1959750485299) X^0 + (-0.000313889819417844) X^1 + (-6.21374144873013E-08) X^2

Line 2 equation: Y = (0.0834768409254421) X^0 + (-0.000105670775146769) X^1 + (1.93568787397805E-07) X^2 + (-1.45541723653532E-12) X^3

1 or 2 Identical Pump Curves in Parallel/Series, and System Curve with intersect point

This app can plot pump curve for 1 or 2 identical pumps running in parallel, as well as a system curve with intersect point. See How-To example.

Final Thought: I wanted to obtain a curve fitting equation from an existing graph image, but I felt powerless to do so. So I created this application, and so on.

>> How To . . .

Related resources: see pump curve scaled plotting program: Pump Curve Scaled Plot

Pay & instant download via PayPal Digital Goods service:

(Note: To click on "Return to Merchant" button after payment at PayPal page for instant download)

CurveFit Tracer

Price: US $2.50

OS requirements: Windows Vista, 7, 8, 10

(Note: this software does not work on Windows XP).

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