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https://issues.apache.org/jira/browse/MATH-1471?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Swinicki updated MATH-1471:
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Description:
Upon performing a bicubic interpolation with two point (x0, y0) and (x1, y1),
the returned bicubic interpolating function returned returns the same result
for variations in the estimated y value.
For example, my inputs are (20, 20) and (25, 25) with f(20, 20) = 64 and f(25,
25) = 6468.
When I get the bicubic interpolating function for this and vary the estimated
x, it works fine. For (21, 20), the function returns 730.016. When I input (20,
21), the function returns 64, which is f(20, 20). For any y value in between 20
and 25, the result is 64. This is the case for any function for which the y
estimate is different from the value on the points.
In other instances, it is varying x values that result in the same result while
varying y estimates seem to work as expected.
was:
Upon performing a bicubic interpolation with two point (x0, y0) and (x1, y1),
the returned bicubic interpolating function returned returns the same result
for variations in the estimated y value.
For example, my inputs are (20, 20) and (25, 25) with f(20, 20) = 64 and f(25,
25) = 6468.
When I get the bicubic interpolating function for this and vary the estimated
x, it works fine. For (21, 20), the function returns 730.016. When I input (20,
21), the function returns 64, which is f(20, 20). For any y value in between 20
and 25, the result is 64. This is the case for any function for which the y
estimate is different from the value on the points.
> BicubicInterpolatingFunction not interpolating correctly for non discrete y
> value
> ---------------------------------------------------------------------------------
>
> Key: MATH-1471
> URL: https://issues.apache.org/jira/browse/MATH-1471
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.6.1
> Environment: JDK 1.8.0_181
> Reporter: Thomas Swinicki
> Priority: Major
>
> Upon performing a bicubic interpolation with two point (x0, y0) and (x1, y1),
> the returned bicubic interpolating function returned returns the same result
> for variations in the estimated y value.
> For example, my inputs are (20, 20) and (25, 25) with f(20, 20) = 64 and
> f(25, 25) = 6468.
> When I get the bicubic interpolating function for this and vary the estimated
> x, it works fine. For (21, 20), the function returns 730.016. When I input
> (20, 21), the function returns 64, which is f(20, 20). For any y value in
> between 20 and 25, the result is 64. This is the case for any function for
> which the y estimate is different from the value on the points.
> In other instances, it is varying x values that result in the same result
> while varying y estimates seem to work as expected.
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