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{alias:function}
h2. Name
*function* — Manipulate data with mathematical expression
h2. Syntax
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*function* _function string_
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h2. Description
The *function* command can be used to manipulate data values in *Polydata* |
Name
function — Manipulate data with mathematical expression
Syntax
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function function string |
Description
The function command can be used to manipulate data values in Polydata (i.e.
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points
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and
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lines)
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and
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Structured
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Points
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(i.e.
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grids).
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The
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specified
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function
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will
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be
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performed
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on
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each
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point
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in
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the
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dataset.
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The
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function
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string
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can
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be
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a
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combination
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of
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several
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sub
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functions
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for
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each
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component
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you
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want
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to
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manipulate.
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Each
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sub
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function
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should
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be
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separated
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with
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a
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semi
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colon
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character
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(
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;
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)
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.
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Each
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sub
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function
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is
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a
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combination
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of
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a
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target
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variable
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,
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an
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equal
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sign
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,
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and
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a
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mathematical
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expression
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.
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for
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example:
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function "x = x + 100 ; y = x + y"
{noformat}
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The
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variables
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in
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the
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function
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are
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always
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from
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the
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original
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dataset.
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In
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the
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example
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above,
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the
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x,
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and
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y
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variable
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in
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the
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second
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sub
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function
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will
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not
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be
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affected
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by
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result
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of
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the
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the
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first
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sub
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function.
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The
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mathematical
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expression
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may
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contain
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these
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operators:
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+,
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-,
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*,
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/,
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abs,
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exp,
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ceil,
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floor,
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ln,
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log10,
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sqrt,
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sin,
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sinh,
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cos,
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cosh,
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tan,
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tanh,
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asin,
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acos,
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atan,
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min,
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max,
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sign.
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A
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conditional
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expression
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is
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also
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supported.
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An
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"if"
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test
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may
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be
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a
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part
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of
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the
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mathematical
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expression.
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The
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syntax
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should
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be
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if(condition,
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result
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if
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true,
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result
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if
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false).
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For
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example:
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function "z = if(z<0, 5, z)"
{noformat}
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will
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replace
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all
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values
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with
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z
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less
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than
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zero
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with
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5.
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Polydata target variables:
x = the x value of the current point
y = the y value of the current point
z = the z value of the current point
s = the scalar value of the current point
Structured Points target variables:
z = the value of the current point.
dx = point spacing in x direction.
dy = point spacing in y direction
origo_x = the X coordinate of the grid origo which is the lower left corner of the Structured Points dataset
origo_y = the Y coordinate of the grid origo which is the lower left corner of the Structured Points dataset
Common Function variables:
The following variables are available to all datasets:
x = the x value of the current point
y = the y value of the current point
z = the z value of the current point
Polydata Function variables:
In addition to the common variables, the following variables are available for polydata
x_ = the x value of the next point
y_ = the y value of the next point
z_ = the z value of the next point
_x = the x value of the previous point
_y = the y value of the previous point
_z = the z value of the previous point
s_ = the scalar value of the previous point
s = the scalar value of the current point
_s = the scalar value of the next point
Structured Points Function variables:
In addition to the common variables, the following variables are available for structured Points
xmin = the x value of the leftmost column of the Structured Points dataset
xmax = the x value of the rightmost column of the Structured Points dataset
ymin = the y value of the uppermost row of the Structured Points dataset
ymax = the y value of the bottommost row of the Structured Points dataset
dx = point spacing in x direction
dy = point spacing in y direction
rows = number of rows
cols = number of columns
origo_x = xmin = the x coordinate of the grid origo which is the lower left corner of the Structured Points dataset
origo_y = ymin = the Y coordinate of the grid origo which is the lower left corner of the Structured Points dataset
Examples:
Example 1: Switch Polydata x and y values
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function "x=y ; y=x"
{noformat}
h4. Example |
Example 2:
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Multiply
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z
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by
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1000
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(Structured
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Points
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or
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Poly
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Data)
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function "z=z*1000"
{noformat}
h4. Example |
Example 3:
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Translate
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polydata
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100
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in
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x
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direction
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function "x=x+100"
{noformat}
h4. Example |
Example 4:
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Translate
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structured
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points
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dataset100
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in
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x
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direction
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function "origo_x=origo_x+100"
{noformat}
h4. Example |
Example 5:
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Use
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formula
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on
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a
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structured
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points
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dataset
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This
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example
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may
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be
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run
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on
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a
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grid.
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It
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will
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replace
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the
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grid
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values
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with
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a
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wave
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pattern.
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Try
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the
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following
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command
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function "z=dy*sin(sqrt(x*x +y*y)/(dx*10))"
{noformat}
h2. See also
[swi - Switch coordinates] , [add - Add to dataset]
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