Guide to Madagascar programs

sfheaderwindow: Window a dataset based on a header mask.

sfheaderwindow mask=head.rsf < in.rsf > out.rsf

The input data is a collection of traces n1xn2,
mask is an integer array os size n2, windowed is n1xm2,
where m2 is the number of nonzero elements in mask.

file	mask=		auxiliary input file name

sfheaderwindow is used to window traces in the input file according to trace header information.

Here is an example of using sfheaderwindow for randomly selecting part of the traces in the input file. First, let us create an input file with ten traces:

bash$ sfmath n1=5 n2=10 output=x2+1 > input.rsf
bash$ < input.rsf sfdisfil
   0:             1            1            1            1            1
   5:             2            2            2            2            2
  10:             3            3            3            3            3
  15:             4            4            4            4            4
  20:             5            5            5            5            5
  25:             6            6            6            6            6
  30:             7            7            7            7            7
  35:             8            8            8            8            8
  40:             9            9            9            9            9
  45:            10           10           10           10           10

Next, we can create a random file with ten header values using sfnoise.

bash$ sfspike n1=10 | sfnoise rep=y type=n > random.rsf
bash$ < random.rsf sfdisfil
   0:     -0.005768      0.02258     -0.04331      -0.4129      -0.3909
   5:      -0.03582       0.4595      -0.3326        0.498      -0.3517

If you reproduce this example, your numbers will most likely be different, because, in the absence of seed= parameter, sfnoise uses a random seed value to generate pseudo-random numbers. Finally, we apply sfheaderwindow to window the input traces selecting only those for which the header is greater than zero.

bash$ < random.rsf sfmask min=0 > mask.rsf
bash$ < mask.rsf sfdisfil
   0:    0    1    0    0    0    0    1    0    1    0
bash$ < input.rsf sfheaderwindow mask=mask.rsf > output.rsf
bash$ < output.rsf sfdisfil
   0:             2            2            2            2            2
   5:             7            7            7            7            7
  10:             9            9            9            9            9

In this case, only three traces are selected for the output. Thanks to the separation between headers and data, the operation of sfheaderwindow is optimally efficient.

Guide to Madagascar programs