[CSC 335] Re: Project Help

[Andrew J. Pounds]

>
> I was confused about the first point under “Here are some particulars” 
> on the handout. The baseline adjustment isn’t what is moving the 
> origin of the spectrum to the most significant peak, correct? If so, 
> what does the baseline adjustment do? I vaguely remember you going 
> over it in class, but I can’t remember exactly what it was used for.
>
>
>
You are correct -- the MOST POSITIVE peak becomes the zero and the 
X-AXIS is shifted based on that.  Shifting the Y-AXIS is a little more 
arbitrary (that is why you have to include it in the input file) but 
hopefully the following will help you see the necessity of doing it.

The following graphs should help...

Here is what one of your raw datafiles might look like...

start



Now -- let's blow this up to look at the y-axis near the baseline.

baseline

Notice that the default baseline (set at zero) is going to pick up a lot 
of spurious peaks.  So -- we will pick an "offset" for our baseline.  In 
this case I will choose 600.

adjusted

This should significantly reduce the amount of "noise" I integrate.  
Now, because I am integrating from only the adjusted baseline to the top 
of the peak, some folks have indicated that it might be easier to simply 
adjust the position of the datafile on the y-axis.  Effectively "shift 
down" the spectral peaks by the baseline value.  If I shift the baseline 
from above -- and all the spectal data - down by 600 it would look like 
the following.

moved

Some claim that this makes it much easier to integrate.


-- 
Andrew J. Pounds, Ph.D.  (pounds at theochem.mercer.edu)
Associate Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627

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