index 74ac4ad40751ad898c783bd0185034c7673a0507..6e31ea6d09916eda496096b02f23acb5ad7d6002 100644 (file)
implicitly, so whenever you specify a number or a variable, it gets
pushed onto the stack automatically.
implicitly, so whenever you specify a number or a variable, it gets
pushed onto the stack automatically.
-At the end of the calculation there should be one and only one
-value left on the stack. This is the outcome of the function and
-this is what is put into the I<vname>. For B<CDEF> instructions,
-the stack is processed for each data point on the graph. B<VDEF>
-instructions work on an entire data set in one run.
+At the end of the calculation there should be one and only one value left on
+the stack. This is the outcome of the function and this is what is put into
+the I<vname>. For B<CDEF> instructions, the stack is processed for each
+data point on the graph. B<VDEF> instructions work on an entire data set in
+one run. Note, that currently B<VDEF> instructions only support a limited
+list of functions.
Example: C<VDEF:maximum=mydata,MAXIMUM>
Example: C<VDEF:maximum=mydata,MAXIMUM>
Example: C<CDEF:mydatabits=mydata,8,*>
This means: push variable I<mydata>, push the number 8, execute
Example: C<CDEF:mydatabits=mydata,8,*>
This means: push variable I<mydata>, push the number 8, execute
-the operator I<+>. The operator needs two elements and uses those
+the operator I<*>. The operator needs two elements and uses those
to return one value. This value is then stored in I<mydatabits>.
As you may have guessed, this instruction means nothing more than
I<mydatabits = mydata * 8>. The real power of B<RPN> lies in the
to return one value. This value is then stored in I<mydatabits>.
As you may have guessed, this instruction means nothing more than
I<mydatabits = mydata * 8>. The real power of B<RPN> lies in the
compute the average of the values v1 to v6 after removing the smallest and
largest.
compute the average of the values v1 to v6 after removing the smallest and
largest.
+B<AVG>
+
+Pop one element (I<count>) from the stack. Now pop I<count> elements and build the
+average, ignoring all UNKNOWN values in the process.
+
+Example: C<CDEF:x=a,b,c,d,4,AVG>
+
B<TREND>
Create a "sliding window" average of another data series.
B<TREND>
Create a "sliding window" average of another data series.
you to make calculations based on the position of the value within
the data set. This function cannot be used in B<VDEF> instructions.
you to make calculations based on the position of the value within
the data set. This function cannot be used in B<VDEF> instructions.
-Z<>
-
=item Time
Time inside RRDtool is measured in seconds since the epoch. The
=item Time
Time inside RRDtool is measured in seconds since the epoch. The
=head1 VARIABLES
=head1 VARIABLES
-These operators work only on B<VDEF> statements.
+These operators work only on B<VDEF> statements. Note that currently ONLY these work for B<VDEF>.
=over 4
=over 4
Example: C<VDEF:perc95=mydata,95,PERCENT>
Example: C<VDEF:perc95=mydata,95,PERCENT>
+=item LSLSLOPE, LSLINT, LSLCORREL
+
+Return the parameters for a B<L>east B<S>quares B<L>ine I<(y = mx +b)>
+which approximate the provided dataset. LSLSLOPE is the slope I<(m)> of
+the line related to the COUNT position of the data. LSLINT is the
+y-intercept I<(b)>, which happens also to be the first data point on the
+graph. LSLCORREL is the Correlation Coefficient (also know as Pearson's
+Product Moment Correlation Coefficient). It will range from 0 to +/-1
+and represents the quality of fit for the approximation.
+
+Example: C<VDEF:slope=mydata,LSLSLOPE>
+
=back
=head1 SEE ALSO
=back
=head1 SEE ALSO
=head1 AUTHOR
=head1 AUTHOR
-Program by Tobias Oetiker E<lt>oetiker@ee.ethz.chE<gt>
+Program by Tobias Oetiker E<lt>tobi@oetiker.chE<gt>
This manual page by Alex van den Bogaerdt E<lt>alex@ergens.op.het.netE<gt>
This manual page by Alex van den Bogaerdt E<lt>alex@ergens.op.het.netE<gt>