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E
ebelmonte1-Visitor
1-Visitor
March 5, 2018
Question

2d linear interpolation

  • March 5, 2018
  • 1 reply
  • 4292 views

Dear all,
I'm facing again a problem with linear 2D interpolation.
In this case I tried to see if the results of direct and inverse interpolation coincide.
z=f(x,y) and y=f(x,z).
Unfortunately, they don't.
Could you please help me in finding the solution of this problem?
Attached you see the mathcad file.

Thank-you very much for your support.

Regards.

Enrico

1 reply

W
Werner_E25-Diamond I
25-Diamond I
March 5, 2018

Sorry, but I see no reason why the two diagrams in your sheet should coincide.

Your first table yields a value for cycles  of 35309 if force=16574 and ratio=0.2.

Your second table suggest a cycle value of just 100 for the same values. Obviously different functions.

 

E
ebelmonte1-VisitorAuthor
1-Visitor
March 6, 2018

Dear Werner,

 

Thank-you very much for your reply.

You are right. I've sorted out the file. Now it should be clearer.

I still find some difficulties by interpolating the data.

I really appreciate your support!

 

Regards.

 

Enrico

 

W
Werner_E25-Diamond I
25-Diamond I
March 6, 2018

OK, I was asking because I was curious if i would be able to calculate and so verify the data tables you provided myself. But obviously I don't have enough information to do so.

 

I have looked at your Excel table pictures and I noticed that the red underlaid values fit pretty well, but the yellow ones don't!  

With Ratio=0,8 and Force=10000, the first table shows cycles=285792

With Ratio=0,8 and Force=10926, the second table shows cycles=100000

This discrepancy may be possible, but may also be a sign the the data tables don't match up.

I can't tell as I am not able to recalculate the data in your two tables.

 

So the reason for the values not being the same may either  be an error in one or both of your data tables, or it can be because your data values are too far apart and linear interpolation is not appropriate - can't decide.

 

BTW, you write that k is the slope of one column in your first data table but when I look at hos curves, they don't seem to be perfect straight lines with a constant slope - not in linear, nor in log scale:

Bild.png

I need the interpolation to get the function N=f(Force,LoadRatio).

 

If you have a way to calculate k for a given Ratio, wouldn't it be simply

Bild2.png

 

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