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Posts: 19
Default Half width

Dear all, I want to known if exist a function that allow me to evaluate the
width of a curve at the half maximun, in other words i have this curve:

547,056 0,36462
547,312 0,92992
547,607 1,5895
547,973 2,42901
548,346 3,27816
549,004 4,82401
549,485 5,93209
549,814 6,68611
549,995 7,09917
550,247 7,66953
550,466 8,14714
550,649 8,53657
550,831 8,91781
551,018 9,28973
551,199 9,65214
551,383 10,0039
551,563 10,3441
551,708 10,6078
551,889 10,9265
552,029 11,1721
552,209 11,4664
552,354 11,691
552,461 11,8532
552,566 12,01
552,709 12,2108
552,814 12,3546
552,921 12,4922
553,063 12,6684
553,204 12,8327
553,344 12,9879
553,484 13,1315
553,588 13,2317
553,728 13,3562
553,866 13,4683
553,969 13,5457
554,072 13,6175
554,177 13,683
554,313 13,7612
554,449 13,827
554,586 13,884
554,721 13,9295
554,857 13,9639
554,958 13,9829
555,091 13,9993
555,226 14,0054
555,36 14,0017
555,492 13,9884
555,622 13,9652
555,755 13,9329
555,887 13,8915
556,054 13,8257
556,187 13,7631
556,319 13,6928
556,447 13,6141
556,61 13,5046
556,772 13,3821
556,935 13,2477
557,064 13,1324
557,224 12,9778
557,385 12,8144
557,546 12,6405
557,707 12,4574
557,868 12,2659
558,059 12,026
558,252 11,7755
558,442 11,5164
558,631 11,2486
558,885 10,8798
559,171 10,4526
559,461 10,0145
559,897 9,31688
560,496 8,35371
560,964 7,58946
561,345 6,98379
561,753 6,33798
562,167 5,70317
562,511 5,17913
562,894 4,6185
563,236 4,11813
563,583 3,6317
563,933 3,15866
564,185 2,82359
564,439 2,49375
564,758 2,09324
565,074 1,70357
565,426 1,28781
565,714 0,95518
566,032 0,59624
566,352 0,24715

and i need to known the width at half maximum?
it is possible?
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Posts: 120
Default Half width

Mauro,

find one of the possible solutions via VBA UDF that gives a straight answer.
Please notice the interpolation between two adjacent points at a halfheight
lever on both branches, it is little more exact than the bare selection of a
single nearest point.

It is, of course, managable by using a series of Excel functions too. Good
school excercise.


Function HalfWidth(X As Variant, Y As Variant) As Double
'..of a single peak.
Dim YHalf As Double, XHalf1 As Double, XHalf2 As Double, I As Long
If X.Count < Y.Count Then Exit Function
YHalf = WorksheetFunction.Max(Y) / 2 'peak halfheight
I = 0
Do
I = I + 1 'seeking the pair of points
If Y(I) YHalf Then 'on the increasing branch
XHalf1 = X(I) + (X(I) - X(I - 1)) / (Y(I) - Y(I - 1)) * (YHalf - Y(I - 1))
Exit Do 'and interpolation for the
intersection
End If 'with YHalf level
Loop
I = X.Count
Do
I = I - 1 'seeking the pair of points
If Y(I) < YHalf Then 'on the decreasing branch
XHalf2 = X(I) + (X(I + 1) - X(I)) / (Y(I + 1) - Y(I)) * (YHalf - Y(I))
Exit Do 'and interpolation for the
intersection
End If 'with YHalf level
Loop
HalfWidth = XHalf2 - XHalf1
End Function


Good luck
--
Petr Bezucha


"Mauro" wrote:

Dear all, I want to known if exist a function that allow me to evaluate the
width of a curve at the half maximun, in other words i have this curve:

547,056 0,36462
547,312 0,92992
547,607 1,5895
547,973 2,42901
548,346 3,27816
549,004 4,82401
549,485 5,93209
549,814 6,68611
549,995 7,09917
550,247 7,66953
550,466 8,14714
550,649 8,53657
550,831 8,91781
551,018 9,28973
551,199 9,65214
551,383 10,0039
551,563 10,3441
551,708 10,6078
551,889 10,9265
552,029 11,1721
552,209 11,4664
552,354 11,691
552,461 11,8532
552,566 12,01
552,709 12,2108
552,814 12,3546
552,921 12,4922
553,063 12,6684
553,204 12,8327
553,344 12,9879
553,484 13,1315
553,588 13,2317
553,728 13,3562
553,866 13,4683
553,969 13,5457
554,072 13,6175
554,177 13,683
554,313 13,7612
554,449 13,827
554,586 13,884
554,721 13,9295
554,857 13,9639
554,958 13,9829
555,091 13,9993
555,226 14,0054
555,36 14,0017
555,492 13,9884
555,622 13,9652
555,755 13,9329
555,887 13,8915
556,054 13,8257
556,187 13,7631
556,319 13,6928
556,447 13,6141
556,61 13,5046
556,772 13,3821
556,935 13,2477
557,064 13,1324
557,224 12,9778
557,385 12,8144
557,546 12,6405
557,707 12,4574
557,868 12,2659
558,059 12,026
558,252 11,7755
558,442 11,5164
558,631 11,2486
558,885 10,8798
559,171 10,4526
559,461 10,0145
559,897 9,31688
560,496 8,35371
560,964 7,58946
561,345 6,98379
561,753 6,33798
562,167 5,70317
562,511 5,17913
562,894 4,6185
563,236 4,11813
563,583 3,6317
563,933 3,15866
564,185 2,82359
564,439 2,49375
564,758 2,09324
565,074 1,70357
565,426 1,28781
565,714 0,95518
566,032 0,59624
566,352 0,24715

and i need to known the width at half maximum?
it is possible?

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Posts: 61
Default Half width

Hello,

Assuming that the x- and y- data are in columns A and B (e.g., A1:A89, and
B1:B89) respectively, enter the following formula in C1 and drag it to fill
the Column C (C1:C89), =IF(B1<MAX($B$1:$B$89)/2," ",ROW())

In some cell, say D1, enter the formula,
=INDIRECT("A"&MAX(C:C))-INDIRECT("A"&MIN(C:C))
Please note that this will not do any interpolation but will estimate the
fwhm from the discrete data points. I think, the estimated fwhm will be
acceptably close to the actual fwhm, if the x-values are closely-spaced.

Best regards,
B.R. Ramachandran

"Mauro" wrote:

Dear all, I want to known if exist a function that allow me to evaluate the
width of a curve at the half maximun, in other words i have this curve:

547,056 0,36462
547,312 0,92992
547,607 1,5895
547,973 2,42901
548,346 3,27816
549,004 4,82401
549,485 5,93209
549,814 6,68611
549,995 7,09917
550,247 7,66953
550,466 8,14714
550,649 8,53657
550,831 8,91781
551,018 9,28973
551,199 9,65214
551,383 10,0039
551,563 10,3441
551,708 10,6078
551,889 10,9265
552,029 11,1721
552,209 11,4664
552,354 11,691
552,461 11,8532
552,566 12,01
552,709 12,2108
552,814 12,3546
552,921 12,4922
553,063 12,6684
553,204 12,8327
553,344 12,9879
553,484 13,1315
553,588 13,2317
553,728 13,3562
553,866 13,4683
553,969 13,5457
554,072 13,6175
554,177 13,683
554,313 13,7612
554,449 13,827
554,586 13,884
554,721 13,9295
554,857 13,9639
554,958 13,9829
555,091 13,9993
555,226 14,0054
555,36 14,0017
555,492 13,9884
555,622 13,9652
555,755 13,9329
555,887 13,8915
556,054 13,8257
556,187 13,7631
556,319 13,6928
556,447 13,6141
556,61 13,5046
556,772 13,3821
556,935 13,2477
557,064 13,1324
557,224 12,9778
557,385 12,8144
557,546 12,6405
557,707 12,4574
557,868 12,2659
558,059 12,026
558,252 11,7755
558,442 11,5164
558,631 11,2486
558,885 10,8798
559,171 10,4526
559,461 10,0145
559,897 9,31688
560,496 8,35371
560,964 7,58946
561,345 6,98379
561,753 6,33798
562,167 5,70317
562,511 5,17913
562,894 4,6185
563,236 4,11813
563,583 3,6317
563,933 3,15866
564,185 2,82359
564,439 2,49375
564,758 2,09324
565,074 1,70357
565,426 1,28781
565,714 0,95518
566,032 0,59624
566,352 0,24715

and i need to known the width at half maximum?
it is possible?

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