PowerLawModel

sans.models.PowerLawModel

Provide F(x) = scale* (x)^(-m) + bkd Power law function as a BaseComponent model

class sans.models.PowerLawModel.PowerLawModel

Bases: sans.models.BaseComponent.BaseComponent

Class that evaluates a Power_Law model.

F(x) = scale* (x)^(-m) + bkd

The model has three parameters:

m = power scale = scale factor bkd = incoherent background

calculate_ER()

clone()

Returns a new object identical to the current object

evalDistribution(qdist)

Evaluate a distribution of q-values.

• For 1D, a numpy array is expected as input:

  evalDistribution(q)

where q is a numpy array.

• For 2D, a list of numpy arrays are expected: [qx_prime,qy_prime], where 1D arrays,

qx_prime = [ qx[0], qx[1], qx[2], ....] and qy_prime = [ qy[0], qy[1], qy[2], ....]

Then get q = numpy.sqrt(qx_prime^2+qy_prime^2)

that is a qr in 1D array; q = [q[0], q[1], q[2], ....]

Note :

Due to 2D speed issue, no anisotropic scattering is supported for python models, thus C-models should have

their own evalDistribution methods.

The method is then called the following way:

evalDistribution(q) where q is a numpy array.

Parameters:

• qdist – ndarray of scalar q-values or list [qx,qy] where qx,qy are 1D ndarrays

getDispParamList()

Return a list of all available parameters for the model

getParam(name)

Set the value of a model parameter

Parameters:

• name – name of the parameter

getParamList()

Return a list of all available parameters for the model

getParamListWithToken(token, member)

getParamWithToken(name, token, member)

is_fittable(par_name)

Check if a given parameter is fittable or not

Parameters:

• par_name – the parameter name to check

run(x=0.0)

Evaluate the model @param x: input q-value (float or [float, float] as [r, theta]) @return: (PowerLaw value)

runXY(x=0.0)

Evaluate the model @param x: input q-value (float or [float, float] as [qx, qy]) @return: PowerLaw value

setParam(name, value)

Set the value of a model parameter

Parameters:

• name – name of the parameter
• value – value of the parameter

setParamWithToken(name, value, token, member)