# Matching two array elements by rounding up and down

2 vues (au cours des 30 derniers jours)
Cemre le 18 Avr 2023
Commenté : Cemre le 19 Avr 2023
Dear mathworks community,
I need to create a conditional array that I find quite challenging. I uploaded an example data list and result that shows what I need to have at the end as both Excel file and txt file.
I have a reference list that is a column vector. It contains numbers from -10 to 10 with step size of 1 as in the uploaded file and I have a secondary list that contains numbers from -10 to 10 again, but the step sizes differ and list B can be shorter than list A. What I need to do is this:
I need to match the elements of two lists by rounding up or down the elements of list B and the below condition should apply:
if |listA(n) – listB(m)| < |listA(n) – listB(m+1)|
listA(n) matches with listB(m).
So each member of listA matches with the closest element of listB.
Also, if there is no closer value of listB(m) to listA(n), then, listB(m) can be used multiple times.
For example,
listA(n) = -5, listA(n+1) = -6 ,
listB(m) = -4.6, listB(m+1) = -5.2, listB(m+2) = -5.8 and listB(m+3) = -6.5
listA(n) - listB(m) = |-5-(-4.6)| = 0.4
listA(n) - listB(m+1) = |-5 – (-5.2)| = 0.2
since 0.2 < 0.4 listA(n) matches with listB(m+1)
and listA(n+1) - listB(m+2) = |-6 – (-5.8)| = 0.2,
listA(n+1) - listB(m+3) = |-6-(-6.5)| = 0.5
so listA(n+1) matches with listB(m+2)
Note: The difference between the elements of list A and list B can be greater than 1, still the same rule applies.
Note2: This is not a homework. I just need to calculate rms of the difference between reference list and secondary list.
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### Réponse acceptée

dpb le 18 Avr 2023
Déplacé(e) : dpb le 18 Avr 2023
ix=isfinite(tT.B);
tT.C=interp1(tT.B(ix),tT.B(ix),tT.A,'nearest','extrap')
tT = 21×3 table
A B C ___ _____ _____ -10 -9.4 -9.4 -9 -7.85 -9.4 -8 -5.6 -7.85 -7 -4.1 -7.85 -6 -2.6 -5.6 -5 -1.1 -5.6 -4 0.4 -4.1 -3 1.9 -2.6 -2 3.4 -2.6 -1 4.9 -1.1 0 6.4 0.4 1 7.9 0.4 2 9.4 1.9 3 NaN 3.4 4 NaN 3.4 5 NaN 4.9
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Cemre le 19 Avr 2023
It really worked. Thank you so much!

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