Python for Science and Engg: Matrices & Least Squares Fit (session4)

Fossee

Description

Python for Science and Engg:Matrices & Least Squares FitFOSSEEDepartment of Aerospace EngineeringIIT BombaySciPy 2010, Introductory tutorialsDay 1, Session 4FOSSEE (IIT Bombay) Matrices & Curve Fitting 1 / 37Outline1 Matrices2 Least Squares Fit3 SummaryFOSSEE (IIT Bombay) Matrices & Curve Fitting 2 / 37MatricesOutline1 Matrices2 Least Squares Fit3 SummaryFOSSEE (IIT Bombay) Matrices & Curve Fitting 3 / 37MatricesMatrices: IntroductionAll matrix operations are done using arraysFOSSEE (IIT Bombay) Matrices & Curve Fitting 4 / 37MatricesMatrices: InitializingIn []: c = array([[11,12,13],[21,22,23],[31,32,33]])In []: cOut[]:array([[11, 12, 13],[21, 22, 23],[31, 32, 33]])FOSSEE (IIT Bombay) Matrices & Curve Fitting 5 / 37MatricesInitializing some special matricesIn []: ones((3,5))Out[]:array([[ 1., 1., 1., 1., 1.],[ 1., 1., 1., 1.,[ 1., 1., 1., 1., 1.]])In []: ones_like([1, 2, 3, 4])Out[]: array([1, 1, 1, 1])In []: identity(2)Out[]:array([[ 1., 0.],[ 0., 1.]])Also availablezeros, zeros_like, empty, empty_likeFOSSEE (IIT Bombay) Matrices & Curve Fitting 6 / 37MatricesAccessing elementsIn []: cOut[]:array([[11, 12, 13],[21, 22, 23],[31, 32, 33]])In []: c[1][2]Out[]: 23In []: c[1,2]Out[]: 23In []: c[1]Out[]: array([21, 22, 23])FOSSEE (IIT Bombay) Matrices & Curve Fitting 7 / 37MatricesChanging elementsIn []: c[1,1] = -22In []: cOut[]:array([[ 11, 12, 13],[ 21, -22, 23],[ 31, 32, 33]])In []: c[1] = 0In []: ...

Sujets

• Python
• Tutoriel
• Calcul (mathématiques)

Informations

• Publié par: mtoledan
• Publié le: 27 juin 2011
• Nombre de lectures: 357
• Langue: English

Extrait

OFSSE

Python for Science and Engg: Matrices & Least Squares Fit

E(IITBom

FOSSEE

Department of Aerospace Engineering IIT Bombay

SciPy 2010, Introductory tutorials Day 1, Session 4

bay)Matrcies&uCrevFitting1/37

Outline

1

2

3

Matrices

Least Squares

Summary

FOSSEE (IIT Bombay)

Fit

Matrices

&

Curve

Fitting

2

/

37

Outline

1

2

3

Matrices

Least Squares

Summary

FOSSEE (IIT Bombay)

Fit

Matrcies

Matrices & Curve Fitting

3 / 37

Matrices:

All

matrix

Intro

operations

FOSSEE (IIT Bombay)

d Ma u

are

rtice c s tion

done

using

Matrices & Curve Fitting

arrays

4 / 37

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13], 23], 33]])

12, 22, 32,

In []: c Out[]: array([[11, [21, [31,

In []: c = array([[11,12,13], [21,22,23], [31,32,33]])

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able zeros, zeros_like, empty,

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In []: ones((3,5)) Out[]: array([[ 1., 1., 1., [ 1., 1., 1., [ 1., 1., 1.,

In []: ones_like([1, 2, 3, 4]) Out[]: array([1, 1, 1, 1])

empty_like

In []: identity(2) Out[]: array([[ 1., 0.], [ 0., 1.]])

1.], 1.], 1.]])

1., 1., 1.,

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13], 23], 33]])

In []: Out[]: In []: Out[]:

c[1][2] 23 c[1,2] 23

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c[1] array([21,

22,

In []: c Out[]: array([[11, 12, [21, 22, [31, 32,

In []: Out[]:

73

23])

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In []: c[1,1] = -22 In []: c Out[]: array([[ 11, 12, [ 21 -22, , [ 31, 32,

How do you access onecumoln?

In []: c[1] = 0 In []: c Out[]: array([[11, 12, 13], [ 0, 0, 0], [31, 32, 33]])

13], 23], 33]])

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In []: c[:,1] Out[]: array([12,

0], 33]])

In []: c[1,:] Out[]: array([0, 0, 0])

0, 32])

7

In []: c[1:3,:] Out[]: array([[ 0, 0, [31, 32,

Slicing

13], 0]])

In []: c[0:2,:] Out[]: array([[11, 12, [ 0, 0,

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13], 0]])

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In []: c[:2,:] Out[]: array([[11, 12, [ 0, 0,

In []: c[1:,:] Out[]: array([[ 0, 0, [31, 32,

0], 33]])

In []: c[1:,:2] Out[]: array([[ 0, 0], [31, 32]])

In []: c[:,::2] Out[]: array([[11, 13], [ 0, 0], [31, 33]])

In []: c[::2,::2] Out[]: array([[11, 13], [31, 33]])

Striding

In []: c[::2,:] Out[]: array([[11, 12, [31, 32,

13], 33]])

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