Difference between revisions of "Scilab/C4/Interpolation/English"
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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 7- Example | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 7- Example | ||
− | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We are given the | + | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We are given the '''natural logarithm''' values for nine, nine point five and eleven. |
− | We have to find the value of natural logarithm of nine point two. | + | We have to find the value of '''natural logarithm''' of nine point two. |
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− | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We define the | + | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We define the '''function Lagrange''' with '''arguments x zero, x, f '''and''' n'''. |
'''X zero''' is the unknown '''interpolation point.''' | '''X zero''' is the unknown '''interpolation point.''' | ||
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'''x''' is the '''vector '''containing the '''data points.''' | '''x''' is the '''vector '''containing the '''data points.''' | ||
− | '''f''' is the '''vector '''containing the values of the '''function '''at | + | '''f''' is the '''vector '''containing the values of the '''function '''at corresponding '''data points.''' |
And '''n '''is the '''order '''of the '''interpolating polynomial'''. | And '''n '''is the '''order '''of the '''interpolating polynomial'''. | ||
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− | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Then we apply '''Lagrange | + | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Then we apply '''Lagrange interpolation formula''' to find the value of the '''numerator''' and '''denominator.''' |
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− | We use '''L''' to find the value of the function '''y''' at the given data point. Finally we display the value of '''L''' and''' f of x.''' | + | We use '''L''' to find the value of the function '''y''' at the given data point. |
+ | |||
+ | |||
+ | Finally we display the value of '''L''' and''' f of x.''' | ||
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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to Scilab console | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to Scilab console | ||
− | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Switch to '''Scilab | + | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Switch to '''Scilab console''' to solve the example problem. |
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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let us define the '''data points vector'''. | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let us define the '''data points vector'''. | ||
− | On the console type, | + | On the '''console''' type, |
'''x equal to open square bracket nine point zero comma nine point five comma eleven point zero close square bracket.''' | '''x equal to open square bracket nine point zero comma nine point five comma eleven point zero close square bracket.''' | ||
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'''f equal to open square bracket two point one nine seven two comma two point two five one three comma two point three nine seven nine close square bracket''' | '''f equal to open square bracket two point one nine seven two comma two point two five one three comma two point three nine seven nine close square bracket''' | ||
− | Press '''Enter''' | + | Press '''Enter'''. |
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'''x zero equal to nine point two''' | '''x zero equal to nine point two''' | ||
− | Press '''Enter''' | + | Press '''Enter'''. |
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Type''' n equal to two''' | Type''' n equal to two''' | ||
− | Press '''Enter''' | + | Press '''Enter'''. |
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− | Press '''Enter''' | + | Press '''Enter'''. |
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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Show console | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Show console | ||
− | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The value of the function '''y''' at '''x | + | | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The value of the function '''y''' at '''x equal to nine point two''' is displayed. |
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− | In spite of this, the same '''interpolating polynomial '''as in '''Lagrange method''' is generated. | + | In spite of this, the same '''interpolating polynomial''', as in '''Lagrange method''', is generated. |
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Revision as of 10:00, 26 December 2013
Title of script: Numerical Interpolation
Author: Shamika
Keywords: Interpolation, Lagrange method, Newton divided difference method
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Slide 1 | Dear Friends,
Welcome to the Spoken Tutorial on “Numerical Interpolation” |
Slide 2 -Learning Objective Slide | At the end of this tutorial, you will learn how to:
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Slide 3-System Requirement slide | To record this tutorial, I am using
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Slide 4- Prerequisites slide | To practise this tutorial, a learner should have
To learn Scilab, please refer to the relevant tutorials available on the Spoken Tutorial website. |
Slide 5- Numerical Interpolation | Numerical interpolation is a method of
We can solve interpolation problems using numerical methods. |
Slide 6- Lagrange Interpolation | In Lagrange interpolation,
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Slide 7- Example | We are given the natural logarithm values for nine, nine point five and eleven.
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Show Lagrange.sci code on Scilab editor | Let us look at the code for Lagrange interpolation. |
Highlight
Lagrange(x0, x,f, n)
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We define the function Lagrange with arguments x zero, x, f and n.
X zero is the unknown interpolation point. x is the vector containing the data points. f is the vector containing the values of the function at corresponding data points. And n is the order of the interpolating polynomial. |
Highlight
m = n + 1; N = ones(1,m);
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We use n to initialize m and vector N.
The order of the interpolating polynomail determines the number of nodes created. |
Highlight
for j = 1:m for k = 1:m if (k<>j) then N(j) = N(j)*(x0 - x(k)) D(j) = D(j)*(x(j) - x(k)) end end
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Then we apply Lagrange interpolation formula to find the value of the numerator and denominator. |
Highlight
L(j) = N(j)/D(j);
end disp(L','L') disp(f,'f(x)')
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Then we divide the numerator and denominator to get the value of L.
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Click on Execute and select Save and Execute | Let us save and execute the file. |
Switch to Scilab console | Switch to Scilab console to solve the example problem. |
Type on console
x=[9.0,9.5,11.0] |
Let us define the data points vector.
On the console type, x equal to open square bracket nine point zero comma nine point five comma eleven point zero close square bracket.
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Type on console
f=[2.1972,2.2513,2.3979] |
Then type
f equal to open square bracket two point one nine seven two comma two point two five one three comma two point three nine seven nine close square bracket Press Enter. |
Type on console
x0=9.2 |
Then type
x zero equal to nine point two Press Enter. |
Type on console
n=2 |
Let us use a quadratic polynomial interpolating polynomial.
Type n equal to two Press Enter. |
Type on console
y = Lagrange(x0, x,f, n) |
To call the function, type
y equal to Lagrange open paranthesis x zero comma x comma f comma n close paranthesis
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Show console | The value of the function y at x equal to nine point two is displayed. |
Let us look at Newton's Divided Difference Method. | |
Slide 8- Newton's Divided Difference Method | In this method, divided differences recursive method is used.
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Slide 9- Example
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Let us solve this example using divided difference method.
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Switch to Scilab editor
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Let us look at the code for Newton Divided difference method.
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style="border-top:n |