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Getting Started with XY Plots - Data From an Equation

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Two commands on the Generate menu are available for generating X,Y values from an equation.


Generates a curve whose amplitudes are a function of X.

X=f(T), Y=g(T)

Generates a curve from parametric equations with X and Y both functions of an independent parameter T. This is particularly useful for generating curves that have multiple Y values for the same X - a circle, for example.

All of the function-parsing routines in DPlot have the same basic syntax, capabilities and limitations:

Available two-side-operators are +, -, *, /, ^. Available one-side operators: sin, cos, tan, asin, acos, atan, abs(absolute value), sqrt(square root), log, logh(or log10), exp (inverse natural logarithm), cosh, sinh, tanh, rnd(random integer; argument is highest number that can be the output), fact(factorial), erf(error function), and cdf(cumulative distribution function). A complete list of available functions is shown here. These all take an argument that must be in parentheses.

By default, angular input values are in radians. You can set angles to degrees by clicking the degrees option button.

DPlot will automatically substitute "PI", "pi", or "Pi" in the function with "4*atan(1.0)"

NOTE: Be specific. DPlot does not interpret "2X" as "2*X".

Prevent divide by zero errors
If this box is unchecked, DPlot will trap divide by zero and many other math errors (e.g. logarithm of a non-positive value), report the value of x where the error occurred, and will not generate a curve. If this box is checked, when DPlot traps a math error it will shift x by a very small number and attempt the calculation again. This feature might be useful for generating curves of certain functions that would normally fail at specific values of x, e.g. sin(x)/x at x=0.



The default scaling for any new XY plot is linear X, linear Y. You can change the scaling (logarithmic X and/or Y, probability scale, polar chart, bar chart, ternary plot, etc.) by right-clicking within the box surrounding the plot and selecting the scaling option from the drop-down menu. Scaling options are also accessible via the Linear/Log Scaling command on the Options menu.

Symbols/Line Types

To change the symbol type or line type used by a curve, right-click on the curve and select the appropriate symbol and/or line type. Alternatively, select the Symbol/Line Styles command on the Options menu.

Scale Extents, Tick Marks, Plot Size

To change the extents of the X or Y axis, change the tick mark interval used, or to change the physical size of the plot, select Options>Extents/Intervals/Size.

Number Format

To change the number format used on any axis (to dates, date and time groups, multiples of PI, powers of 10, etc.), right-click on any of those numbers and select the appropriate format. To specify that a 1000 separator should be used, to specify the number of decimal places used, or to change the orientation of those numbers, right-click on any of those numbers and select “More number format options...”. Alternatively select the Number Formats command on the Options menu.



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