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Graphing a Function

The Chart & List Window offers a convenient function graphing facility.

Select Function Graph from the window's Chart menu to show the function graph, as shown below.

DreamCalc Function Graphing

Function Input

To plot a function of the form y = f(x):

1. Type your function into the entry box, using "x" to specify the variable.
2. Specify the x-value range in the MIN and MAX boxes.
3. Press return, or click the "Enter" button.

Alternatively, rather than hitting return to input your function, you may create a dual plot by designating your input as either plot "A" or "B". Click the drop-down arrow next to the "Enter" button to do this. See below.

Enter as Plot A or B

The input expression is not case sensitive, and the prefix "y=" is not necessary. The maximum graphing numerical range is: -1E100 < x or y < 1E100. Complex numbers are not supported in graphing.

Available Functions

The following functions are available for use with graphing functions:

Operators: ^, +, -, *, /, %, !
Variables: x, t

You can use the Axes menu to show logarithmic axes or to map your plot on to a polar grid.

Parametric Variable

You may use the parametric variable "t" in your input expression in place of "x". In this case, DreamCalc will generate a Polar Plots.

Graphing Angle Mode

The Function Graph has it's own angle mode, as indicated by the radio buttons in the top right of the window. This angle mode is independent of the calculator's main angle mode. It defines the operation of the trigonometric functions when the function plot is created. After changing the angle mode, you must re-input your function by clicking Enter.

Specifying the Range

Prior to plotting your function, you should specify the desired range of x using the MIN/MAX range edit boxes. You may use simple expressions in the range boxes, such as: "0.86 * PI".

Alternatively, you may specify the range as part of the function input string itself—using square brackets and a semi-colon " ; " as the separator.

For example:

sin(x) [0; PI/2]

DreamCalc will strip off the range values and fill out the range boxes for you when the function is entered. You must, however, specify the interval separately in the Interval or No. Points edit box (see right).

If you use a period "." as your decimal point you may, if you wish, use a comma as the separator instead of semi-colon.

Setting No. Points or Interval

DreamCalc needs to know how many data points to generate. You can specify this using:

Specify No. Points
Allows you to specify the number of points, where the corresponding interval will be calculated automatically. Generally this option is more convenient, as you do not have to re-define the interval for every function plot. However, it doesn't offer precise control of the values generated as x-inputs to your plot.

Specify Interval
Allows you to specify an interval, giving you precise control over the x values used as input to your expression. For example, if your range is [0; 10] and you specify an interval value of 1, points will be generated at integers x = 0, 1, 2, 3... up to and including 10, or eleven points in total. If your input range and interval define a number of points greater than the maximum number of permissible points, the interval will be adjusted so as to limit the number of points.

Error Conditions

If no plot could be generated, an applicable error will be shown in the graphing display area.

A plot will be generated, however, if two or more y-value results were successfully calculated over the input range—even if many other points could not be determined. Often this is to be expected from the nature of the input; for example, no x-y point will be plotted for the input expression "1 / x" at x=0. In such cases, DreamCalc will display a small warning message in the graphing area to indicate that not all points were generated, but otherwise the plot will be shown as normal.

Output to X-Y List

When the Output to X-Y List option is checked, chart data is copied to the X-Y list at the time the plot is generated. You may then edit or export the chart data from the Data List page tab of the window.

The effect of the Output to X-Y List option is to overwrite the X-Y list each time you generate a function plot. If you accidently overwrite your list, simply go to the list page tab and click undo to recover the your original data.

Lengthy Calculations

Generally plots will be generated instantly. However, lengthy functions and/or a high number of data points may cause DreamCalc to timeout, generating only a partial plot over the desired input range. By default, DreamCalc will timeout on graphing operations after approximately 5 seconds. You can increase this in Options Window by setting the Timeout option to a value greater than this.

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