Meaning of InterpolationOrder -> All for multidimensional interpolation Planned maintenance...

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Meaning of InterpolationOrder -> All for multidimensional interpolation



Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
Announcing the arrival of Valued Associate #679: Cesar Manara
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8












$begingroup$


What specific method does Interpolation use for unstructured multi-dimensional data when we set InterpolationOrder -> All? Documentation links are welcome.



Example 2D data:



data = RandomReal[1, {20, 3}];


When the data points are not on a grid, the only allowed settings for InterpolationOrder are 1 and All, according to the error message issued when trying something else.



With 1, it is clear how it works: a Delaunay triangulation is computed and linear interpolation is done over each triangle.



But how does All work, and what determines the actual order that is chosen?



if = Interpolation[data, InterpolationOrder -> All];

if["InterpolationOrder"]
(* 5 *)

Show[
Plot3D[if[x, y], {x, 0, 1}, {y, 0, 1}],
Graphics3D[{PointSize[Large], Point[data]}]
]


enter image description here










share|improve this question









$endgroup$












  • $begingroup$
    Dunno, but the return value of if["InterpolationOrder"] that I get is {9223372036854775806, 9223372036854775806}. Oo
    $endgroup$
    – Henrik Schumacher
    21 hours ago






  • 1




    $begingroup$
    @HenrikSchumacher Oops ... It seems I tried this with M12.0 (it's available in the cloud).
    $endgroup$
    – Szabolcs
    21 hours ago






  • 1




    $begingroup$
    Anyways, very good questions. I am also curious what works there in the background.
    $endgroup$
    – Henrik Schumacher
    21 hours ago










  • $begingroup$
    @HenrikSchumacher If this gives a hint, starting from 4 data points, the first 3 data point counts get interpolation order 2, then the next 4 get 3, then the next 5 get 4, etc.
    $endgroup$
    – Szabolcs
    21 hours ago






  • 1




    $begingroup$
    That sounds as if they were using straight-forward global interpolation by a polynomial of degree up to n. Then you have Binomial[n, 2] basis functions. In that case, this should become nasty for higher point counts due to Runge's phenomenon and ill-conditioned linear systems (for solving for the coefficients). So I presume, that they will switch to another method when the point count becomes larger...
    $endgroup$
    – Henrik Schumacher
    21 hours ago


















8












$begingroup$


What specific method does Interpolation use for unstructured multi-dimensional data when we set InterpolationOrder -> All? Documentation links are welcome.



Example 2D data:



data = RandomReal[1, {20, 3}];


When the data points are not on a grid, the only allowed settings for InterpolationOrder are 1 and All, according to the error message issued when trying something else.



With 1, it is clear how it works: a Delaunay triangulation is computed and linear interpolation is done over each triangle.



But how does All work, and what determines the actual order that is chosen?



if = Interpolation[data, InterpolationOrder -> All];

if["InterpolationOrder"]
(* 5 *)

Show[
Plot3D[if[x, y], {x, 0, 1}, {y, 0, 1}],
Graphics3D[{PointSize[Large], Point[data]}]
]


enter image description here










share|improve this question









$endgroup$












  • $begingroup$
    Dunno, but the return value of if["InterpolationOrder"] that I get is {9223372036854775806, 9223372036854775806}. Oo
    $endgroup$
    – Henrik Schumacher
    21 hours ago






  • 1




    $begingroup$
    @HenrikSchumacher Oops ... It seems I tried this with M12.0 (it's available in the cloud).
    $endgroup$
    – Szabolcs
    21 hours ago






  • 1




    $begingroup$
    Anyways, very good questions. I am also curious what works there in the background.
    $endgroup$
    – Henrik Schumacher
    21 hours ago










  • $begingroup$
    @HenrikSchumacher If this gives a hint, starting from 4 data points, the first 3 data point counts get interpolation order 2, then the next 4 get 3, then the next 5 get 4, etc.
    $endgroup$
    – Szabolcs
    21 hours ago






  • 1




    $begingroup$
    That sounds as if they were using straight-forward global interpolation by a polynomial of degree up to n. Then you have Binomial[n, 2] basis functions. In that case, this should become nasty for higher point counts due to Runge's phenomenon and ill-conditioned linear systems (for solving for the coefficients). So I presume, that they will switch to another method when the point count becomes larger...
    $endgroup$
    – Henrik Schumacher
    21 hours ago
















8












8








8





$begingroup$


What specific method does Interpolation use for unstructured multi-dimensional data when we set InterpolationOrder -> All? Documentation links are welcome.



Example 2D data:



data = RandomReal[1, {20, 3}];


When the data points are not on a grid, the only allowed settings for InterpolationOrder are 1 and All, according to the error message issued when trying something else.



With 1, it is clear how it works: a Delaunay triangulation is computed and linear interpolation is done over each triangle.



But how does All work, and what determines the actual order that is chosen?



if = Interpolation[data, InterpolationOrder -> All];

if["InterpolationOrder"]
(* 5 *)

Show[
Plot3D[if[x, y], {x, 0, 1}, {y, 0, 1}],
Graphics3D[{PointSize[Large], Point[data]}]
]


enter image description here










share|improve this question









$endgroup$




What specific method does Interpolation use for unstructured multi-dimensional data when we set InterpolationOrder -> All? Documentation links are welcome.



Example 2D data:



data = RandomReal[1, {20, 3}];


When the data points are not on a grid, the only allowed settings for InterpolationOrder are 1 and All, according to the error message issued when trying something else.



With 1, it is clear how it works: a Delaunay triangulation is computed and linear interpolation is done over each triangle.



But how does All work, and what determines the actual order that is chosen?



if = Interpolation[data, InterpolationOrder -> All];

if["InterpolationOrder"]
(* 5 *)

Show[
Plot3D[if[x, y], {x, 0, 1}, {y, 0, 1}],
Graphics3D[{PointSize[Large], Point[data]}]
]


enter image description here







interpolation






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked 21 hours ago









SzabolcsSzabolcs

164k14448950




164k14448950












  • $begingroup$
    Dunno, but the return value of if["InterpolationOrder"] that I get is {9223372036854775806, 9223372036854775806}. Oo
    $endgroup$
    – Henrik Schumacher
    21 hours ago






  • 1




    $begingroup$
    @HenrikSchumacher Oops ... It seems I tried this with M12.0 (it's available in the cloud).
    $endgroup$
    – Szabolcs
    21 hours ago






  • 1




    $begingroup$
    Anyways, very good questions. I am also curious what works there in the background.
    $endgroup$
    – Henrik Schumacher
    21 hours ago










  • $begingroup$
    @HenrikSchumacher If this gives a hint, starting from 4 data points, the first 3 data point counts get interpolation order 2, then the next 4 get 3, then the next 5 get 4, etc.
    $endgroup$
    – Szabolcs
    21 hours ago






  • 1




    $begingroup$
    That sounds as if they were using straight-forward global interpolation by a polynomial of degree up to n. Then you have Binomial[n, 2] basis functions. In that case, this should become nasty for higher point counts due to Runge's phenomenon and ill-conditioned linear systems (for solving for the coefficients). So I presume, that they will switch to another method when the point count becomes larger...
    $endgroup$
    – Henrik Schumacher
    21 hours ago




















  • $begingroup$
    Dunno, but the return value of if["InterpolationOrder"] that I get is {9223372036854775806, 9223372036854775806}. Oo
    $endgroup$
    – Henrik Schumacher
    21 hours ago






  • 1




    $begingroup$
    @HenrikSchumacher Oops ... It seems I tried this with M12.0 (it's available in the cloud).
    $endgroup$
    – Szabolcs
    21 hours ago






  • 1




    $begingroup$
    Anyways, very good questions. I am also curious what works there in the background.
    $endgroup$
    – Henrik Schumacher
    21 hours ago










  • $begingroup$
    @HenrikSchumacher If this gives a hint, starting from 4 data points, the first 3 data point counts get interpolation order 2, then the next 4 get 3, then the next 5 get 4, etc.
    $endgroup$
    – Szabolcs
    21 hours ago






  • 1




    $begingroup$
    That sounds as if they were using straight-forward global interpolation by a polynomial of degree up to n. Then you have Binomial[n, 2] basis functions. In that case, this should become nasty for higher point counts due to Runge's phenomenon and ill-conditioned linear systems (for solving for the coefficients). So I presume, that they will switch to another method when the point count becomes larger...
    $endgroup$
    – Henrik Schumacher
    21 hours ago


















$begingroup$
Dunno, but the return value of if["InterpolationOrder"] that I get is {9223372036854775806, 9223372036854775806}. Oo
$endgroup$
– Henrik Schumacher
21 hours ago




$begingroup$
Dunno, but the return value of if["InterpolationOrder"] that I get is {9223372036854775806, 9223372036854775806}. Oo
$endgroup$
– Henrik Schumacher
21 hours ago




1




1




$begingroup$
@HenrikSchumacher Oops ... It seems I tried this with M12.0 (it's available in the cloud).
$endgroup$
– Szabolcs
21 hours ago




$begingroup$
@HenrikSchumacher Oops ... It seems I tried this with M12.0 (it's available in the cloud).
$endgroup$
– Szabolcs
21 hours ago




1




1




$begingroup$
Anyways, very good questions. I am also curious what works there in the background.
$endgroup$
– Henrik Schumacher
21 hours ago




$begingroup$
Anyways, very good questions. I am also curious what works there in the background.
$endgroup$
– Henrik Schumacher
21 hours ago












$begingroup$
@HenrikSchumacher If this gives a hint, starting from 4 data points, the first 3 data point counts get interpolation order 2, then the next 4 get 3, then the next 5 get 4, etc.
$endgroup$
– Szabolcs
21 hours ago




$begingroup$
@HenrikSchumacher If this gives a hint, starting from 4 data points, the first 3 data point counts get interpolation order 2, then the next 4 get 3, then the next 5 get 4, etc.
$endgroup$
– Szabolcs
21 hours ago




1




1




$begingroup$
That sounds as if they were using straight-forward global interpolation by a polynomial of degree up to n. Then you have Binomial[n, 2] basis functions. In that case, this should become nasty for higher point counts due to Runge's phenomenon and ill-conditioned linear systems (for solving for the coefficients). So I presume, that they will switch to another method when the point count becomes larger...
$endgroup$
– Henrik Schumacher
21 hours ago






$begingroup$
That sounds as if they were using straight-forward global interpolation by a polynomial of degree up to n. Then you have Binomial[n, 2] basis functions. In that case, this should become nasty for higher point counts due to Runge's phenomenon and ill-conditioned linear systems (for solving for the coefficients). So I presume, that they will switch to another method when the point count becomes larger...
$endgroup$
– Henrik Schumacher
21 hours ago












1 Answer
1






active

oldest

votes


















7












$begingroup$

This is code that has been written many moons ago... first an example:



d = {{0.4138352728412389, 0.02365673668161028}, {0.5509946389658635, 
0.7254061374370833}, {0.14521595926324116,
0.6528630823305817}, {0.48768962246740544,
0.22066264105073286}, {0.8309710560928056,
0.3496966364384875}, {0.4553589220242207,
0.9383446951847001}, {0.2126873262146789,
0.017512080396716145}, {0.967248982535015,
0.6211273372083488}, {0.3548669163916416,
0.737108322193581}, {0.6919974835480842, 0.9322403408098401}};
f = {{0.9953617542392983}, {0.14070666511222818},
{0.285662339441511}, {0.7988192898854105}, {0.3592646208757597},
{0.565455746009103}, {0.22110814761432618}, {0.2735048548887764},
{0.08792348530403005}, {0.4202942851818514}};
data = Join[d, f, 2];
if = Interpolation[data, InterpolationOrder -> All];
if[0.5, 0.5]

0.268157


And here is roughly what it does:



dt = Transpose[d];
temp = Join[{ConstantArray[1., {Length[d]}]}, dt, dt[[{1}]]^2,
dt[[{1}]]*dt[[{2}]], dt[[{2}]]^2, dt[[{1}]]^3,
dt[[{1}]]^2*dt[[{2}]], dt[[{1}]]*dt[[{2}]]^2, dt[[{2}]]^3];
p = Transpose[temp];
ls = LinearSolve[p];
vals = ls[Flatten[f]];
System`Private`EvaluateListPolynomial[vals, {0.5, 0.5}]

0.268157





share|improve this answer









$endgroup$














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    1 Answer
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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    7












    $begingroup$

    This is code that has been written many moons ago... first an example:



    d = {{0.4138352728412389, 0.02365673668161028}, {0.5509946389658635, 
    0.7254061374370833}, {0.14521595926324116,
    0.6528630823305817}, {0.48768962246740544,
    0.22066264105073286}, {0.8309710560928056,
    0.3496966364384875}, {0.4553589220242207,
    0.9383446951847001}, {0.2126873262146789,
    0.017512080396716145}, {0.967248982535015,
    0.6211273372083488}, {0.3548669163916416,
    0.737108322193581}, {0.6919974835480842, 0.9322403408098401}};
    f = {{0.9953617542392983}, {0.14070666511222818},
    {0.285662339441511}, {0.7988192898854105}, {0.3592646208757597},
    {0.565455746009103}, {0.22110814761432618}, {0.2735048548887764},
    {0.08792348530403005}, {0.4202942851818514}};
    data = Join[d, f, 2];
    if = Interpolation[data, InterpolationOrder -> All];
    if[0.5, 0.5]

    0.268157


    And here is roughly what it does:



    dt = Transpose[d];
    temp = Join[{ConstantArray[1., {Length[d]}]}, dt, dt[[{1}]]^2,
    dt[[{1}]]*dt[[{2}]], dt[[{2}]]^2, dt[[{1}]]^3,
    dt[[{1}]]^2*dt[[{2}]], dt[[{1}]]*dt[[{2}]]^2, dt[[{2}]]^3];
    p = Transpose[temp];
    ls = LinearSolve[p];
    vals = ls[Flatten[f]];
    System`Private`EvaluateListPolynomial[vals, {0.5, 0.5}]

    0.268157





    share|improve this answer









    $endgroup$


















      7












      $begingroup$

      This is code that has been written many moons ago... first an example:



      d = {{0.4138352728412389, 0.02365673668161028}, {0.5509946389658635, 
      0.7254061374370833}, {0.14521595926324116,
      0.6528630823305817}, {0.48768962246740544,
      0.22066264105073286}, {0.8309710560928056,
      0.3496966364384875}, {0.4553589220242207,
      0.9383446951847001}, {0.2126873262146789,
      0.017512080396716145}, {0.967248982535015,
      0.6211273372083488}, {0.3548669163916416,
      0.737108322193581}, {0.6919974835480842, 0.9322403408098401}};
      f = {{0.9953617542392983}, {0.14070666511222818},
      {0.285662339441511}, {0.7988192898854105}, {0.3592646208757597},
      {0.565455746009103}, {0.22110814761432618}, {0.2735048548887764},
      {0.08792348530403005}, {0.4202942851818514}};
      data = Join[d, f, 2];
      if = Interpolation[data, InterpolationOrder -> All];
      if[0.5, 0.5]

      0.268157


      And here is roughly what it does:



      dt = Transpose[d];
      temp = Join[{ConstantArray[1., {Length[d]}]}, dt, dt[[{1}]]^2,
      dt[[{1}]]*dt[[{2}]], dt[[{2}]]^2, dt[[{1}]]^3,
      dt[[{1}]]^2*dt[[{2}]], dt[[{1}]]*dt[[{2}]]^2, dt[[{2}]]^3];
      p = Transpose[temp];
      ls = LinearSolve[p];
      vals = ls[Flatten[f]];
      System`Private`EvaluateListPolynomial[vals, {0.5, 0.5}]

      0.268157





      share|improve this answer









      $endgroup$
















        7












        7








        7





        $begingroup$

        This is code that has been written many moons ago... first an example:



        d = {{0.4138352728412389, 0.02365673668161028}, {0.5509946389658635, 
        0.7254061374370833}, {0.14521595926324116,
        0.6528630823305817}, {0.48768962246740544,
        0.22066264105073286}, {0.8309710560928056,
        0.3496966364384875}, {0.4553589220242207,
        0.9383446951847001}, {0.2126873262146789,
        0.017512080396716145}, {0.967248982535015,
        0.6211273372083488}, {0.3548669163916416,
        0.737108322193581}, {0.6919974835480842, 0.9322403408098401}};
        f = {{0.9953617542392983}, {0.14070666511222818},
        {0.285662339441511}, {0.7988192898854105}, {0.3592646208757597},
        {0.565455746009103}, {0.22110814761432618}, {0.2735048548887764},
        {0.08792348530403005}, {0.4202942851818514}};
        data = Join[d, f, 2];
        if = Interpolation[data, InterpolationOrder -> All];
        if[0.5, 0.5]

        0.268157


        And here is roughly what it does:



        dt = Transpose[d];
        temp = Join[{ConstantArray[1., {Length[d]}]}, dt, dt[[{1}]]^2,
        dt[[{1}]]*dt[[{2}]], dt[[{2}]]^2, dt[[{1}]]^3,
        dt[[{1}]]^2*dt[[{2}]], dt[[{1}]]*dt[[{2}]]^2, dt[[{2}]]^3];
        p = Transpose[temp];
        ls = LinearSolve[p];
        vals = ls[Flatten[f]];
        System`Private`EvaluateListPolynomial[vals, {0.5, 0.5}]

        0.268157





        share|improve this answer









        $endgroup$



        This is code that has been written many moons ago... first an example:



        d = {{0.4138352728412389, 0.02365673668161028}, {0.5509946389658635, 
        0.7254061374370833}, {0.14521595926324116,
        0.6528630823305817}, {0.48768962246740544,
        0.22066264105073286}, {0.8309710560928056,
        0.3496966364384875}, {0.4553589220242207,
        0.9383446951847001}, {0.2126873262146789,
        0.017512080396716145}, {0.967248982535015,
        0.6211273372083488}, {0.3548669163916416,
        0.737108322193581}, {0.6919974835480842, 0.9322403408098401}};
        f = {{0.9953617542392983}, {0.14070666511222818},
        {0.285662339441511}, {0.7988192898854105}, {0.3592646208757597},
        {0.565455746009103}, {0.22110814761432618}, {0.2735048548887764},
        {0.08792348530403005}, {0.4202942851818514}};
        data = Join[d, f, 2];
        if = Interpolation[data, InterpolationOrder -> All];
        if[0.5, 0.5]

        0.268157


        And here is roughly what it does:



        dt = Transpose[d];
        temp = Join[{ConstantArray[1., {Length[d]}]}, dt, dt[[{1}]]^2,
        dt[[{1}]]*dt[[{2}]], dt[[{2}]]^2, dt[[{1}]]^3,
        dt[[{1}]]^2*dt[[{2}]], dt[[{1}]]*dt[[{2}]]^2, dt[[{2}]]^3];
        p = Transpose[temp];
        ls = LinearSolve[p];
        vals = ls[Flatten[f]];
        System`Private`EvaluateListPolynomial[vals, {0.5, 0.5}]

        0.268157






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 19 hours ago









        user21user21

        20.2k45487




        20.2k45487






























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