This error message typically occurs when using a function fitting library, such as scipy.optimize.curve_fit, and it means that the data passed to the function as the "y" values (often referred to as ydata) does not have the same length as the values generated by the function being fit to the data (referred to as the "function value").
To fix this error, you will need to make sure that the ydata passed to the function has the same length as the function values. This could mean adjusting the size of your input data, or adjusting the function you are fitting to the data so that it generates output of the same length as the ydata.
Another thing you can do is to adjust the parameter bounds, sometimes the optimization algorithm is not able to find a solution within the given bounds, try to adjust the bounds or remove them.
Additionally, make sure that the input to the function being fit to the data is of the correct size and shape, and that it matches the xdata passed to the function. If the function being fit to the data expects a 2D array as input, for example, make sure that the input data is also in that format.
Another possible cause of the error could be that the function being fit to the data is not defined for certain values of the input data. This could happen, for example, if the function is only defined for positive values of x and the input data includes negative values. In such a case, you will need to either adjust the input data so that it only includes valid values for the function, or adjust the function itself so that it can handle the input data as it is.
It could also be that the function is not returning values or returning None. Double check the function to make sure it's returning something.
If you have tried all of these suggestions and are still having trouble, it may be helpful to post the code you are using along with the specific error message you are receiving, so that others can help you troubleshoot the issue.
https://www.reddit.com/r/matlab/comments/78mxg9/error_using_lsqcurvefit_function_value_and_ydata/
Frequently Asked Questions About Function Value And Ydata Sizes Are Not Equal.
What does this error message mean?
This error message typically occurs when using a function fitting library, such as scipy.optimize.curve_fit, and it means that the data passed to the function as the "y" values (often referred to as ydata) does not have the same length as the values generated by the function being fit to the data (referred to as the "function value").
How can I fix this error?
To fix this error, you will need to make sure that the ydata passed to the function has the same length as the function values. This could mean adjusting the size of your input data, or adjusting the function you are fitting to the data so that it generates output of the same length as the ydata.
What could be the reason for this error?
Possible reasons for this error could be that the input data passed to the function is of the wrong size or shape, that the function is not defined for certain values of the input data, or that the function is not returning any values or returning None.
Why my input data is correct but still getting the error?
you can try to adjust the parameter bounds, sometimes the optimization algorithm is not able to find a solution within the given bounds, try to adjust the bounds or remove them.
How can I check if the ydata and function values are of the same size?
You can use the python built-in function len() to check the length of the ydata and function values. If they are not equal, then the error is likely caused by a mismatch in the sizes of these two arrays.
I'm using a library function, is there any way to check if the ydata and function values are of the same size?
Yes, you can use the python built-in function len() to check the length of the ydata and the output of the function. Additionally, some library functions also have built-in checks for the size of the input data and will raise an error if the sizes do not match.
I'm getting the error even though the ydata and function values are of the same size, why?
The error message might be misleading, and the problem could be in the function or in the input data. It's recommended to print out the shapes of both the ydata and the function values to ensure that they match, and to check that your input data is being passed to the function correctly.
I'm using a custom function, how can I make sure that it's returning the correct size of output?
When defining a custom function, you should make sure that the function returns output of the same size as the input data. Additionally, you should test your function by passing it different inputs and checking the output size to make sure it's consistent.
I'm using a custom function, how can I make sure that it's defined for all the values of the input data?
When defining a custom function, you should make sure that the function is defined for all the values of the input data. If the function is only defined for certain values, you should include a check in the function to handle such cases or filter out the input data that causes problem.