Matrix problem

ruby-talk
1

i have a matrix :remember=Matrix[ [] ]
and this line remember[0,0]=3
why do i have this error at that line: undefined method `[]=' for
Matrix[[]]:Matrix (NoMethodError)

and how do i set values for my matrix only with one row

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2

Bulhac Mihai wrote:

i have a matrix :remember=Matrix[ ]
and this line remember[0,0]=3
why do i have this error at that line: undefined method `=' for
Matrix[]:Matrix (NoMethodError)

and how do i set values for my matrix only with one row

Matrix is immutable, so there is no method = to assign values.
= is the method called in remember[0,0]=3, it is just syntax sugar for
remember.=(0,0,3).

Maybe you want nested arrays instead.

Regards
Stefan

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3

i have a matrix :remember=Matrix[ ]
and this line remember[0,0]=3
why do i have this error at that line: undefined method `=' for
Matrix[]:Matrix (NoMethodError)

and how do i set values for my matrix only with one row

Hmm. It appears Matrix objects are supposed to be immutable. Use
arrays instead and convert to Matrix for matrix-type functions, so ...

require 'matrix'

=> true

require 'mathn' #need this for correct determinant calculations

=> true

a = [[1, 2], [3, 4]]

=> [[1, 2], [3, 4]]

a[0][0] = 3

=> [[3, 2], [3, 4]]

m = Matrix[*a]

=> Matrix[[3, 2], [3, 4]]

m.transpose

=> Matrix[[3, 3], [2, 4]]

m * m

=> Matrix[[15, 14], [21, 22]]

m_float = m.map {|i| i.to_f}

=> Matrix[[3.0, 2.0], [3.0, 4.0]]

m_inv = m_float.inverse

=> Matrix[[0.666666666666667, -0.333333333333333], [-0.5, 0.5]]

m.to_a

=> [[0.666666666666667, -0.333333333333333], [-0.5, 0.5]]

hth,
Todd

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On 7/12/07, Bulhac Mihai <mihai.bulhac@yahoo.com> wrote: