s_impedance.m

地震、测井方面matlab代码,解释的比较详细

function impedance=s_impedance(refl,scale)
% Function computes impedance from reflection coefficients
% Start time and sample interval of the output impedance is that
% of the reflection coefficients
% Method used: Recursive computation from reflectivity
% See also: s_refl2impedance
% Written by E. R.: February 14, 2002
% Last update: April 1, 2002: Handle multi-trace input
%
%           impedance=s_impedance(refl,scale)
% INPUT 
% impedance Impedance in form of a seismic structure
% scale     Scale information. Either a seismic structure with an impedance
%           trace or a scalar representing the impedance at the first sample
%           of the output. In the former case the number of samples of 
%           scale.trace must equal 1 + the number of samples of refl.trace.   
% 
% OUTPUT
% refl        Reflection coefficient sequence
%                     refl=s_reflcoeff(impedance)

[nsamp,ntr]=size(refl.traces);
temp=(1+refl.traces)./(1-refl.traces);
temp=[ones(1,ntr);cumprod(temp)];
if isnumeric(scale)
  impedance.traces=scale*temp;
  htext=['First impedance value is ',num2str(scale)];

elseif isstruct(scale)
  if length(scale.traces) ~= length(temp)
    error(' Traces in "scale" and "impedance" do not have the same number of samples')
  end
  temp1=log(scale.traces./temp);
  idx=~isnan(temp1);
  a=exp(median(temp1(idx)));
  impedance.traces=a*temp;
  htext='Impedance scaled to reference';
else
  error(' Illegal variable for "scale"')
end

%	Check for NaNs
index=find(isnan(impedance.traces));
if ~isempty(index)
  refl.null=NaN;
end
impedance.last=refl.last+refl.step;

%       Copy rest of fields
impedance=copy_fields(refl,impedance);

%    Append history field
if isfield(refl,'history')
  impedance=s_history(impedance,'append',htext);
end