Confused by output from Polyval
up vote
1
down vote
favorite
I have some data from which I have fitted a 2nd order polynomial using numpy.polynomial.polynomial.polyfit
data_fit = poly.polyfit(length_spline_a, temp_spline_b, 2)
I am examining changes in length, and have a list of 10% changes in length
len_steps = 0.0, -0.012573565669572757, -0.025147131339145513, -0.03772069700871827...
print (len(len_steps)
>>>>11
My assumption was that polyval would solve for y for each of the x values in the len_steps list
y_data = poly.polyval(data_fit, len_steps)
However this provides a list with only 3 data points rather than the 11 I expected.
print(y_data)
>>>>[-5.34112443e+21 -2.50395581e+28 -6.75169134e+28]
Have I mis understood the purpose of polyval or have I done something wrong?
python python-3.x numpy polynomials
asked Nov 8 at 10:46
nick.sculthorpe
507
add a comment |
up vote
1
down vote
favorite
I have some data from which I have fitted a 2nd order polynomial using numpy.polynomial.polynomial.polyfit
data_fit = poly.polyfit(length_spline_a, temp_spline_b, 2)
I am examining changes in length, and have a list of 10% changes in length
len_steps = 0.0, -0.012573565669572757, -0.025147131339145513, -0.03772069700871827...
print (len(len_steps)
>>>>11
My assumption was that polyval would solve for y for each of the x values in the len_steps list
y_data = poly.polyval(data_fit, len_steps)
However this provides a list with only 3 data points rather than the 11 I expected.
print(y_data)
>>>>[-5.34112443e+21 -2.50395581e+28 -6.75169134e+28]
Have I mis understood the purpose of polyval or have I done something wrong?
python python-3.x numpy polynomials
asked Nov 8 at 10:46
nick.sculthorpe
507
add a comment |
up vote
1
down vote
favorite
up vote
1
down vote
favorite
I have some data from which I have fitted a 2nd order polynomial using numpy.polynomial.polynomial.polyfit
data_fit = poly.polyfit(length_spline_a, temp_spline_b, 2)
I am examining changes in length, and have a list of 10% changes in length
len_steps = 0.0, -0.012573565669572757, -0.025147131339145513, -0.03772069700871827...
print (len(len_steps)
>>>>11
My assumption was that polyval would solve for y for each of the x values in the len_steps list
y_data = poly.polyval(data_fit, len_steps)
However this provides a list with only 3 data points rather than the 11 I expected.
print(y_data)
>>>>[-5.34112443e+21 -2.50395581e+28 -6.75169134e+28]
Have I mis understood the purpose of polyval or have I done something wrong?
python python-3.x numpy polynomials
asked Nov 8 at 10:46
nick.sculthorpe
507
I have some data from which I have fitted a 2nd order polynomial using numpy.polynomial.polynomial.polyfit
data_fit = poly.polyfit(length_spline_a, temp_spline_b, 2)
I am examining changes in length, and have a list of 10% changes in length
len_steps = 0.0, -0.012573565669572757, -0.025147131339145513, -0.03772069700871827...
print (len(len_steps)
>>>>11
My assumption was that polyval would solve for y for each of the x values in the len_steps list
y_data = poly.polyval(data_fit, len_steps)
However this provides a list with only 3 data points rather than the 11 I expected.
print(y_data)
>>>>[-5.34112443e+21 -2.50395581e+28 -6.75169134e+28]
Have I mis understood the purpose of polyval or have I done something wrong?
python python-3.x numpy polynomials
python python-3.x numpy polynomials
asked Nov 8 at 10:46
nick.sculthorpe
507
asked Nov 8 at 10:46
nick.sculthorpe
507
edited Nov 8 at 11:16
asked Nov 8 at 10:46
nick.sculthorpe
507
asked Nov 8 at 10:46
nick.sculthorpe
507
asked Nov 8 at 10:46
nick.sculthorpe
507
507
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
up vote
0
down vote
The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.
answered Nov 8 at 11:26
nick.sculthorpe
507
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.
answered Nov 8 at 11:26
nick.sculthorpe
507
add a comment |
up vote
0
down vote
The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.
answered Nov 8 at 11:26
nick.sculthorpe
507
add a comment |
up vote
0
down vote
up vote
0
down vote
The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.
answered Nov 8 at 11:26
nick.sculthorpe
507
The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.
answered Nov 8 at 11:26
nick.sculthorpe
507
answered Nov 8 at 11:26
nick.sculthorpe
507
answered Nov 8 at 11:26
nick.sculthorpe
507
answered Nov 8 at 11:26
nick.sculthorpe
507
507
add a comment |
add a comment |
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53206124%2fconfused-by-output-from-polyval%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
