Editing Guide to madagascar programs (section)

==sfheadercut==
{| class="wikitable" align="center" cellspacing="0" border="1"
! colspan="4" style="background:#ffdead;" | Zero a portion of a dataset based on a header mask.
|-
! colspan="4" | sfheadercut mask=head.rsf < in.rsf > out.rsf
|-
|  colspan="4" | <br>The input data is a collection of traces n1xn2,<br>mask is an integer array of size n2.
|-
| ''file   '' || '''mask=''' ||   || 	auxiliary input file name
|}

<tt>sfheadercut</tt> is close to <tt>sfheaderwindow</tt> but instead
of windowing the dataset, it fills the traces specified by the header
mask with zeroes. The size of the input data is preserved.
Here is an example of using <tt>sfheaderwindow</tt> for 
zeroing every other trace in the input file. First, let us create
an input file with ten traces:
<pre>
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
</pre>
Next, we can create a mask with alternating ones and zeros using
<tt>sfinterleave</tt>.
<pre>
bash$ sfspike n1=5 mag=1 | sfdd type=int > ones.rsf
bash$ sfspike n1=5 mag=0 | sfdd type=int > zeros.rsf
bash$ sfinterleave axis=1 ones.rsf zeros.rsf > mask.rsf
bash$ sfdisfil < mask.rsf
   0:    1    0    1    0    1    0    1    0    1    0
</pre>
Finally, <tt>sfheadercut</tt> zeros the input traces.
<pre>
bash$ sfheadercut < input.rsf mask=mask.rsf > output.rsf
bash$ sfdisfil < output.rsf 
   0:             1            1            1            1            1
   5:             0            0            0            0            0
  10:             3            3            3            3            3
  15:             0            0            0            0            0
  20:             5            5            5            5            5
  25:             0            0            0            0            0
  30:             7            7            7            7            7
  35:             0            0            0            0            0
  40:             9            9            9            9            9
  45:             0            0            0            0            0
</pre>