mathcomesalive

Welcome to FLOWCALC, by Howard Phillips

a data flow graphical programming tool for the evaluation of formulae, algebraic expressions, recurrence relations and simple first order dynamical systems.

Inspired by many years of using MATLAB/Simulink, used by professional engineers the world over, I have developed a much simplified version for use in schools to help students understand what is going on in any calculation process and how that process can be represented in a flow diagram with inputs, connectors and a final output.

Here is a very simple Flowcalc model, in which the three inputs, a, b and x, are combined to give the output y. Inspection reveals that the relationship between inputs and output is

y = ax + b

A single evaluation takes the values given to the inputs and delivers the output. When repeat evaluation is requested the inputs a and b are treated as constants, but the x input value changes at each repeat according to specified start value and step length. The resulting sequence of pairs (x,y) is plotted on a graph, one point at a time, at a low, medium or high speed.

The output value at each connector can be displayed and watched as it changes.

There are no subtraction or division operations; these are done by placing a sign change connector or a reciprocal connector in the input path.

In the basic state the diagram is constructed from the following:

Simple algebraic expressions and formulae can be constructed and evaluated, and an insight into the evaluation process will be gained. The difference between constants (those inputs whose values the user changes) and variables (those inputs whose values are changed automatically) becomes quite apparent.

Quadratic expressions can be constructed, even cubics, but these get rather complicated.

The advanced state has many more connectors

With numerical integration (trapezoidal rule) and differentiation (approximating parabola method), a delay function and a summation function many different processes can be modeled.

This is the cubic

and this is the resulting plot, in progress. Finished plots show in blue without the points. Plots are accumulated on the grid until “clear” is clicked.

Construction of the flow diagram is very straightforward.

Firstly the inputs and connectors and the output are placed on the grid.

Secondly names are given to the inputs and the output.

Then the boxes are selected to be linked; the lines are drawn automatically.

Finally the model is operated, as single run or repeat.

Any of these actions can be carried out at any time. The flow diagram can be copied to the clipboard for editing, printing etc.

The panel shown headed “You are placing now” is one of several help panels, all of which can be hidden when no longer needed.

Details for 3D_comesalive will be ready soon

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