Hello Dr. King,

I am using CEM on for a small pilot study and I am new to historical control matching methodologies. I am interested in using k-to-k matching to draw a matched sample from people who have completed a specific clinical program. I ran the following code and the CEM software seemingly performs the k-to-k match:

mat3.1 <- cem(treatment = "Intervention", data = PP, drop = todrop3, keep.all = TRUE)

matk2k3.1 <- k2k(mat3.1, PP, method = euclidean, 1)

matk2k3.1

G0 G1

All 185 15

Matched 15 15

Unmatched 170 0

However, I also get the following warning: "Error in k2k(mat3.1, PP, euclidean, 1) : object 'euclidean' not found"

Moreover, I also get:

mat3.1$k2k

[1] FALSE

I was wondering if you had any advice regarding why I am getting this warning and the 'False' indication regarding the match? My concern is that the match may not be completed correctly.

Thank you,

Chris