scipy curve_fit error: Result from function call is not a proper array of floats

I have an [x,y] dataset and I would like to fit a function to it. This are x and y ``` parang = np.array([ 61.1725 , 62.140625, 62.93275 , 63.701625, 65.89225 , 66.476875, 68.33525 , 68.902375, 72.03975 , 72.590375, 73.144125, 73.670625, 80.36525 , 80.80275 , 87.505375, 87.90375 , 100.557875, 100.8915 ]) q = np.array([-0.03699417, -0.03451252, -0.03851238, -0.0393034 , -0.04059193, -0.03941371, -0.04206476, -0.04153004, -0.04721763, -0.04667099, -0.03996427, -0.03872865, -0.05054322, -0.0466561 , -0.05476921, -0.05274144, -0.0474299 , -0.04974607]) ``` and then I want to fit a function to the data that goes as follows: ``` def fq(x,bq,cuq): qval = bq*stndqu[0]*np.cos(np.radians(2*x))+cuq*stndqu[1]*np.sin(np.radians(2*x)) print qval print qval.dtype return qval ``` where 'bq,cuq' are the parameter I need to fit and stndqu are global parameters I obtain as: ``` stnd = input(r'P ($\%$) and $\theta$ of pol. standard? (as tuple)') p = stnd[0]/100. ang = np.radians(stnd[1]) x,y = sympy.symbols('x y') stndqu = sympy.solve([sympy.sqrt(x**2+y**2)-p,(0.5*sympy.atan(y/x))-ang],[x,y])[1] ``` and P and theta are 2.73 and 95. The stndqu[0] and stndqu[1] I get out from that block are 0.0272334985720932 and 0.00190435173321445 To find the parameters 'bq' and 'cuq' of the function that fit my data I do: ``` qpopt,pconv = scio.curve_fit(fq, parang, q) ``` and here's the result: ``` [-0.0129614827538107 -0.0137658898997091 -0.0144124082012406 -0.0150294169782742 -0.0167265263727253 -0.0171633151430064 -0.0185034265676582 -0.0188971421096823 -0.0209373417940197 -0.0212701779430718 -0.0215969783128203 -0.0219002154908251 -0.0250793309165333 -0.0252411052388773 -0.0269646924974054 -0.0270214005655701 -0.0260909416985902 -0.0259956074319825] object [-0.0129614827538107 -0.0137658898997091 -0.0144124082012406 -0.0150294169782742 -0.0167265263727253 -0.0171633151430064 -0.0185034265676582 -0.0188971421096823 -0.0209373417940197 -0.0212701779430718 -0.0215969783128203 -0.0219002154908251 -0.0250793309165333 -0.0252411052388773 -0.0269646924974054 -0.0270214005655701 -0.0260909416985902 -0.0259956074319825] object --------------------------------------------------------------------------- TypeError Traceback (most recent call last) TypeError: array cannot be safely cast to required type --------------------------------------------------------------------------- error Traceback (most recent call last) /Users/mj/Documents/NACO/VLT/DataReduction/<ipython-input-57-cac353117232> in <module>() ----> 1 qpopt,pconv = scio.curve_fit(fq, parang, q) /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/scipy/optimize/minpack.pyc in curve_fit(f, xdata, ydata, p0, sigma, **kw) 408 # Remove full_output from kw, otherwise we're passing it in twice. 409 return_full = kw.pop('full_output', False) --> 410 res = leastsq(func, p0, args=args, full_output=1, **kw) 411 (popt, pcov, infodict, errmsg, ier) = res 412 /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/scipy/optimize/minpack.pyc in leastsq(func, x0, args, Dfun, full_output, col_deriv, ftol, xtol, gtol, maxfev, epsfcn, factor, diag, warning) 268 if (maxfev == 0): 269 maxfev = 200*(n+1) --> 270 retval = _minpack._lmdif(func,x0,args,full_output,ftol,xtol,gtol,maxfev,epsfcn,factor,diag) 271 else: 272 if col_deriv: error: Result from function call is not a proper array of floats. ``` I tried specifying the type of the qval element making it ``` def fq(x,bq,cuq): qval = np.array( bq*stndqu[0]*np.cos(np.radians(2*x))+cuq*stndqu[1]*np.sin(np.radians(2*x)), dtype=float) ``` and then the result changes to: ``` qpopt = scio.curve_fit(fq, parang, q) [-0.01296148 -0.01376589 -0.01441241 -0.01502942 -0.01672653 -0.01716332 -0.01850343 -0.01889714 -0.02093734 -0.02127018 -0.02159698 -0.02190022 -0.02507933 -0.02524111 -0.02696469 -0.0270214 -0.02609094 -0.02599561] float64 [-0.01296148 -0.01376589 -0.01441241 -0.01502942 -0.01672653 -0.01716332 -0.01850343 -0.01889714 -0.02093734 -0.02127018 -0.02159698 -0.02190022 -0.02507933 -0.02524111 -0.02696469 -0.0270214 -0.02609094 -0.02599561] float64 --------------------------------------------------------------------------- TypeError Traceback (most recent call last) TypeError: array cannot be safely cast to required type --------------------------------------------------------------------------- error Traceback (most recent call last) /Users/mj/Documents/NACO/VLT/DataReduction/<ipython-input-50-1f4d3764f7ae> in <module>() ----> 1 qpopt = scio.curve_fit(fq, parang, q) /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/scipy/optimize/minpack.pyc in curve_fit(f, xdata, ydata, p0, sigma, **kw) 408 # Remove full_output from kw, otherwise we're passing it in twice. 409 return_full = kw.pop('full_output', False) --> 410 res = leastsq(func, p0, args=args, full_output=1, **kw) 411 (popt, pcov, infodict, errmsg, ier) = res 412 /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/scipy/optimize/minpack.pyc in leastsq(func, x0, args, Dfun, full_output, col_deriv, ftol, xtol, gtol, maxfev, epsfcn, factor, diag, warning) 268 if (maxfev == 0): 269 maxfev = 200*(n+1) --> 270 retval = _minpack._lmdif(func,x0,args,full_output,ftol,xtol,gtol,maxfev,epsfcn,factor,diag) 271 else: 272 if col_deriv: error: Result from function call is not a proper array of floats. ``` So no progress... Can someone tell me where is this going wrong? Thank you very much in advance! M.