Shortcut: MATHEVAL

Module	function
Description	Usage
An alias to the CUSTOM function that can also be used to calaculate combinations of variables using a custom expression.
output value	type
an arbitrary function	scalar/vector/matrix/grid

Input

The arguments that serve as the input for this action are specified using one or more of the keywords in the following table.

Further details and examples

An alias to the CUSTOM function that can also be used to calaculate combinations of variables using a custom expression.

The documentation for this action is identical to that for CUSTOM. You can thus use it to evaluate a evaluate an arbitrary function as in the following example input:

Click on the labels of the actions for more information on what each action computes

dABThe DISTANCE action with label dAB calculates the following quantities:
 Quantity   
 Type   
 Description  
dAB
scalar
the DISTANCE between this pair of atoms: DISTANCECalculate the distance/s between pairs of atoms. More details ATOMSthe pair of atom that we are calculating the distance between=10,12
dACThe DISTANCE action with label dAC calculates the following quantities:
 Quantity   
 Type   
 Description  
dAC
scalar
the DISTANCE between this pair of atoms: DISTANCECalculate the distance/s between pairs of atoms. More details ATOMSthe pair of atom that we are calculating the distance between=10,15
diffThe MATHEVAL action with label diff calculates the following quantities:
 Quantity   
 Type   
 Description  
diff
scalar
an arbitrary function: MATHEVALAn alias to the CUSTOM function that can also be used to calaculate combinations of variables using a custom expression. More details ARGthe values input to this function=dAB,dAC FUNCthe function you wish to evaluate=y-x PERIODICif the output of your function is periodic then you should specify the periodicity of the function=NO
# notice: the previous line could be replaced with the following
# diff: COMBINE ARG=dAB,dAC COEFFICIENTS=-1,1
METADUsed to performed metadynamics on one or more collective variables. More details ARGthe labels of the scalars on which the bias will act=diff SIGMAthe widths of the Gaussian hills=0.1 HEIGHTthe heights of the Gaussian hills=0.5 BIASFACTORuse well tempered metadynamics and use this bias factor=10 PACEthe frequency for hill addition=100

This alias is kept in order to maintain compatibility with previous PLUMED versions. However, notice that as of PLUMED 2.5 the libmatheval library is not linked anymore, and that the MATHEVAL action evaluates functions the Lepton library.

\par Examples

Just replace \ref CUSTOM with \ref MATHEVAL.

\plumedfile d: DISTANCE ATOMS=10,15 m: MATHEVAL ARG=d FUNC=0.5step(0.5-x)+xstep(x-0.5) PERIODIC=NO

check the function you are applying:

PRINT ARG=d,m FILE=checkme RESTRAINT ARG=d AT=0.5 KAPPA=10.0 \endplumedfile (see also \ref DISTANCE, \ref PRINT, and \ref RESTRAINT)

References

More information about how this action can be used is available in the following articles: - A. Pérez-Villa, M. Darvas, G. Bussi, ATP dependent NS3 helicase interaction with RNA: insights from molecular simulations. Nucleic Acids Research. 43, 8725–8734 (2015)

Syntax

The following table describes the keywords and options that can be used with this action