simple_manipulations.md



Simple manipulations
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In this tutorial session, we will learn some basic data manipulations:
selecting, binning, reorganizing. We use the same test data set as
before (see the introduction of the tutorial).

A simple manipulation: delete some spectra
Launch Frida in the directory that contains the test data set, and
perform the following actions one by one. Take your time to understand
Frida's reaction to each single command. To do so, use the inspection
and plot commands you learned in session 1.
command          action                                             recommended inspection

? > fl gly180   load one data file

0 > msd 0:3     manipulate_spectra_delete: delete spectra 0 to 3

1 > 0:1 dz      inspect old and new file
In general, manipulations leave the original file intact; they act upon
a copy of the file that is stored at the end of the internal memory,
with a new internal file number. In this example, a manipulation on file
0 yielded a new file 1.

Average spectra

0:1 > 1 msa 0,3,6   manipulate_spectra_add: average over groups of spectra: spectra 0 to 2 become new spectrum 0; spectra 3 to 5 become new spectrum 1; spectra 6 to 8 become new spetrum 2
2 > 1 msa ::3       short-hand for the same: ::3 means every third, starting from 0

Use dz to see the effect of the binning. Use plot commands to verify
that the averaged spectra have better statistics than the original ones.

Delete files from internal memory
From now on, directory and plot commands are no longer prescribed in the
listings. Use them on your own to investigate the effects of the
manipulations introduced in the following. Try also variations of the
commands presented here.
Your activities will create new files in the internal memory. To clean
up, and to restore standard conditions for the next example, use the
deletion command:

1: > fdel   deletes all inline files starting with file 1

In the following, we always assume that file 0 is gly180 as read from
disk.

Bin channels

0 > mpa ::3   manipulate-points-add: within each spectrum, bin three data points into one

Plot input and output to see the improved statistics after binning.

Reduce dimension

? > 0 msa 0   average all spectra into one
? > 0 msr 6   manipulate-spectra-retain: delete all spectra except spectrum 6

Each of these two commands creates a file that contains just one
spectrum. Use the inspection commands df, dc, dr to see the effect of
this dimension reduction: z0 is automatically converted into a rpar.

Merge files, and save to disk

? > : fdel      empty the internal memory (or start new Frida session)
? > fl gly???   load five test files
0:4 > msr 6     retain spectrum 6 of each file
5:9 > mfj       manipulate-file-join: merge five files into one
10 > dz         old rpar has become z0
10 > fs         save to disk, using the autogenerated file name gly
10 > mpa ::3    channel binning, as explained above
11 > fso        save, overwriting the existing file gly

Last updated for Frida2.3.0c.