Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_math”.

  FT_MATH performs mathematical operations on FieldTrip data structures,
  such as addition, subtraction, division, etc.
 
  Use as
    data = ft_math(cfg, data1, data2, ...)
  with one or multiple FieldTrip data structures as the input and the configuration
  structure cfg in which you specify the mathematical operation that is to be
  executed on the desired parameter from the data
    cfg.parameter = string, field from the input data on which the operation is
                    performed, e.g. 'pow' or 'avg'
    cfg.operation = string, for example '(x1-x2)/(x1+x2)' or 'x1/6'
 
  In the specification of the mathematical operation, x1 is the parameter obtained
  from the first input data structure, x2 from the second, etc.
 
  Rather than specifying the operation as a string that is evaluated, you can also
  specify it as a single operation. The advantage is that it is computed faster.
     cfg.operation = string, can be 'add', 'subtract', 'divide', 'multiply', 'log10', 'abs'
  If you specify only a single input data structure and the operation is 'add',
  'subtract', 'divide' or 'multiply', the configuration should also contain:
    cfg.scalar    = scalar value to be used in the operation
 
  The operation 'add' is implemented as follows
    y = x1 + x2 + ....
  if you specify multiple input arguments, or as
    y = x1 + s
  if you specify one input argument and a scalar value.
 
  The operation 'subtract' is implemented as follows
    y = x1 - x2 - ....
  if you specify multiple input arguments, or as
    y = x1 - s
  if you specify one input argument and a scalar value.
 
  The operation 'divide' is implemented as follows
    y = x1 ./ x2
  if you specify two input arguments, or as
    y = x1 / s
  if you specify one input argument and a scalar value.
 
  The operation 'multiply' is implemented as follows
    y = x1 .* x2
  if you specify two input arguments, or as
    y = x1 * s
  if you specify one input argument and a scalar value.
 
  To facilitate data-handling and distributed computing you can use
    cfg.inputfile   =  ...
    cfg.outputfile  =  ...
  If you specify one of these (or both) the input data will be read from a *.mat
  file on disk and/or the output data will be written to a *.mat file. These mat
  files should contain only a single variable, corresponding with the
  input/output structure.
 
  See also FT_DATATYPE