为什么我的python lmfit minimumsq拟合函数传递了太多参数？

Question

I've tried to search for someone making the same mistake as me, but have had no joy! It's also my 1st post, so I apologise if it's badly explained or directed. Advice welcome.

The problem I am solving is: Finding the position of a receiver of some kind by measuring the distances to a number of known reference points. It's basic trilateration, and I am using least squares to do this.

I have successfully used the scipy.optimize lesatsq function already to do this, so I'm pretty sure my fitting function works. However, I want to be able to use some of the extra features that the lmfit Python package offers, and I'm struggling to translate it accross. Full attempt code is here: http://pastebin.com/4xbfkaCm

The lmfit minimize function sets up calls to my fitting function, (which is called residualfunct) as follows, with stationarray being a numpy array containing station locations and ranges and params being a dictionary of parameters to be used in the fitting function

position = minimize(residualfunct, params, args=(stationarray))

and my fitting function is defined as

def residualfunct(params, stationarray):

    X = params['solutionX'].value
    Y = params['solutionY'].value
    Z = params['solutionZ'].value
    result = numpy.array([s[3] - linalg.norm(array((X,Y,Z))-array((s[0],s[1],s[2]))) for s in stationarray])
    print result
    return result

When I run this code I get the TypeError:

residualfunct() takes exactly 2 arguments (5 given).

as this call is made by the minimize function, I don't see what control I have over this. I can only imagine that this is being raised because I am passing an np.array as an argument, but this seems unavoidable. Can anyone see what I am doing wrong?

Thanks

Answer 1

In the call to minimize , change

args=(stationarray)

to

args=(stationarray,)

args must be a sequence (typically a tuple) whose elements are the arguments passed to the function. To create a tuple of length 1, you need the extra comma. When you write args=(stationarray) (without the extra comma), the parentheses have no effect, and it is the same as writing args=stationarray . minimize then calls the function as residualfunct(params, stationarray[0], stationarray[1], ...) , which results in the error that you reported.