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Basic operations to make your life easier when using FRIDA1

Here there are some commands or “tricks” to make your life easier when using FRIDA. Of course you van look at the commands help (hc). What we will try to do here is the counter part: if I have a problem: which command(s) should I use???

Plotting

  • A trick to plot every 4 spectra, just type p *i4

Fitting

  • After finishing fitting, how can I quickly see the fits together with the data I have already displayed?
    • Type “a”, then the program will “add” the plots for the fittings…
  • I get strange spikes (exactly where the exp. points are) when plotting fitted curves!
    • This is a bug in the “online” convolution with the vanadium measurement. You have to convolve “by hand” using cg, then set the displaystyle to line with eg and add with a.
  • I have done a fitting to several files (i.e. W as a function of Q2), I have extracted the coefficients of the fitting (therefore I have a lot of files with only one value related to the temperature) and now I want to put all them in one file, and plot them as a function of temperature… If the files with one value resulting for the fitting are from number 1 to 10:
1-10 the files with one extracted value resulting from the fitting
mfj we will put all the values in one single file. This file will have 10 “spectra” with one only value… and I want to have one spectra with all the values. Therefore
msxwill exchange the values of z (the spectra) and x. BUT sometimes you will get the error message: x ↔ z makes no sense if there are several z's. Tha is because (of course) because internally the program has got several z's Then:
ez we will see if that is true, you should get only one column, if not:
d to delete one z coordinate
2 the number 2, for example
d sometimes you will have also to delete another one
2 which after deleting the former is now number 2
enter to go out form the menu
msx and now you can at last have one nice file with your values as a function of temperature!!!!

Redistributing data or the joy of mgr

Once we have some file we would like to redistrivute the data and put them in a regular grid (for example from (q,w) or w in a logarithmic scala…), how to do it? As an example we will “put the data” in a x logarithmic grid.

mgr to redistribute the data
3 because we want to redistribute in a logarithmic scala (1 for a linear one!!!), if you want to make linear for a determined range, and log for another range use option 2
1e10 for the first value (it is so big because in our case was a frequency in Hz…)
1e13 for the last value
10 I want 10 point per decade. In the case of a linear grid the increment of x axis will be asked
3 What happens if there are not enough experimental points to “fill” the grid. with option 3 the program will fill the whole grid, also if there are no experimental points, repeating the value of the closer point. Option 2 will not fill the whole grid with points… just test it!!!
here you have it!!!

Making a master curve

I have a lot of (nice) spectra, and I would like to make a master curve, that is to say, I would like to divide (multiply) each spectra by a number, to match all the curves in one… I suppose that the spectra are in file 1

oi to select “integral” options
9 wit this option you will “rescale” all the curves from a file in one. with option 11 you will match spectra from different files
n/y do you want to “calculate” the coefficients for the rescaling using the same x-rang for all the curves? let's asume that you answered y
* all the range for average
1 the rescaling coef for curve 1 will be 1
1 I will save the coeffs in a file… then the program will generate a file (number 2 in this case)with a point per spectra, which is the rescaling factor, and now I want to dicide each spectra by this factor
1 I will operate on file 1
oy I will operate on y axis
/I will divide by the factor in the file
i The second argument will be one value per spectra taken from another file
2from file 2, where I have my rescaling factors

And now a new file with your rescaled curves is created.