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**pltf** provides a simple way to use **bc**(1)
and **plt**(1)
to generate plots of many common functions of a single variable. The command-line
arguments are interpreted according to their position; **pltf** asks for values
for any missing arguments.

The first argument, *expression*, can be any expression
valid as input to **bc**(1)
, with the additional feature that the variable
**x** may appear anywhere in the expression where a number would be allowed
by **bc**. Some examples of valid expressions are:

**x^3+3*x^2+3*x+1****(x + 1)^3****s(sqrt(x^2))**

The first two of these are equivalent; note that whitespace and parentheses
are allowed in expressions, although it is necessary to enclose such expressions
in double quotes (e.g., **"(x + 1)*e(x)"**) when entering them as command-line
arguments in order to protect them from the shell. The last expression
is the sine of the square root of x squared; see **bc**(1)
for a complete
list of available special functions, or invoke **pltf** with no command-line
arguments to obtain a list.

The second and third arguments specify the domain
of the function (the values over which **x** should vary), and the fourth argument
specifies the **x**-increment (the difference between consecutive values of
**x** for which the expression is to be evaluated).

**pltf** is a shell script that
uses a helper application, **ftable**, to prepare input for **bc -l**. Invoke **ftable**
directly (using the same arguments as for **pltf**) if you need to change the
format of the plot or make a printed version of it. See the source for
**pltf** to see how to do this.

**http://www.physionet.org/physiotools/plt/plt/misc/pltf**

**http://www.physionet.org/physiotools/plt/plt/misc/ftable.c**

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Updated 13 August 2012