How do I use specifyCoefficients with a vectorized conductivity c?

I am trying to use the solvepde function to solve an elliptic PDE and return the solution and its gradient. To do this I need to use the specifyCoefficients function to specify the coefficients in the model. My problem arises when trying to use a vector for the conductivity coefficient c. In the given (2-D) application I have a vector, that is the conductivity evaluated at the nodes of the PDE mesh, but I do not have a function for c. The code snippet looks as follows:

m = m(:);
model = prob_data.fwd_model;
p = prob_data.Meshdata.points;
t = prob_data.Meshdata.triangles;
c = exp(m);
c = pdeintrp(p,t,c);
specifyCoefficients(model,'m',0,'d',0,'c',c,'a',0,'f',@myffun);
forward_solve = solvepde(fwd_model);

This causes the following error:

% Error using pde.CoefficientAssignment/checkCCoefSize (line 429)
% Size of the matrix 'c' is not consistent with
% the pde.PDEModel/PDESystemSize property.

I have tried letting c be a vector the size of the mesh nodes, and also tried interpolating c to evaluate it at the center of the triangles of the mesh as in the code above. I have also looked at the documentation https://www.mathworks.com/help/pde/ug/c-coefficient-for-systems-for-specifycoefficients.html . Based on the documentation it looks like I may need to elongate the vector by repeating its values several times to represent the elements of a tensor. The documentation here is rather confusing to me and I haven't been able to get specifyCoefficients to work, any help clarifying this would be much appreciated.

-Isaac