Hi,

My name is Cephas Ablakwa, and I am a PH.D. student studying in Program Planning and Evaluation in education. I am working on my dissertation, hoping to defend in June 2020. While using the CEM package in R, I ran into an issue that I hope you can help me with.  When automating a progressive coarsening procedure using the relax.cem function, I got the following error: Error1:n : argument of length 0. After googling the issue extensively, I found an answer to a similar error (but with a different function) that suggested there might be a matrix with "one dimension of length 1, without drop=FALSE, R converts a matrix to a vector." The solution offered to this similar problem was lengthy, complex, and specific to the issue. Given my level of experience with R, I do not know how to extrapolate this solution to my issue. In my field and at my university, we mainly use SPSS. I have taken up R mainly to use your CEM package and explore causal inference and coarsened exact matching in my work. I have tried multiple solutions, including restructuring the class of my variables to resemble the class structure of the LeLonde dataset used in the example.

Find attached is a summary of the initial steps I took to arrive at the error. I could provide more information if you need it. Any help you can offer will be greatly appreciated. I hope to hear from you soon.