CS 451 Quiz 3
Model and cost function; Linear algebra with Octave / Matlab
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Model and Cost Function
What is
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The ith elements of vectors x and y
The ith test input
The ith training example
(x, y) to the ith power
What does the hypothesis function h attempt?
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To predict X from Y
To predict Y from X
To model X without knowing Y
To model Y without knowing X
Consider the following cost function J:
Check all that are true
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J measures how well h_theta(xi) predicts outputs yi
J computes the mean squared error between inputs xi and outputs yi
Required
The goal of linear regression is to
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Find J such that Theta0, Theta1 are minimized
Find Theta0, Theta1 such that J is minimized
Compute the derivative of J wrt. the error
Gradient Descent
In the above plot, what does the vertical axis represent?
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Theta0
Theta1
The cost J
If the above function is minimized with gradient descent, the solution could depend on: (check all that apply)
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The starting point
The learning rate alpha
Required
Linear algebra with Octave / Matlab
Consider the following problems in Octave / Matlab notation. Recall that [1, 2, 3] is a row vector, [1; 2; 3] is a column vector, and x' is the transpose of x.
If v = [2, 3, 4], what is v'?
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[4, 3, 2]
[2; 3; 4]
[4; 3; 2]
none of the above
If v = [2, 3, 4] and w = [2, 1, 1], what is v  w ?
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[0, 2, 5]
[0, 2, 5]
[0; 2; 5]
not a valid operation
If v = [2, 3, 4] and w = [2, 1, 1], what is w'  v' ?
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[0, 2, 5]
[0, 2, 5]
[0; 2; 5]
not a valid operation
If v = [2, 3, 4] and w = [2, 1, 1], what is v * w' ?
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0
3
9
a 3 x 3 matrix
not a valid operation
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