Writer IDs cannot contain letters

[stephaniereinders]

Describe the bug If the writer IDs in the filenames of the model training documents contain letters, fit_model() produces the error:

To Reproduce Steps to reproduce the behavior:

1. Created a folder called "handwriter_demo" on my desktop. Created a folder called "data" inside the "handwriter_demo" folder. Created a folder called "model_docs" inside the "data" folder.
2. Copied a cluster template "template.rds" into the "data" folder
3. Copied the following handwriting samples from the CSAFE Handwriting database into the model_docs folder:

   [1] "w0009_s01_pWOZ_r01.png" "w0009_s01_pWOZ_r02.png" "w0009_s01_pWOZ_r03.png"
   [4] "w0030_s01_pWOZ_r01.png" "w0030_s01_pWOZ_r02.png" "w0030_s01_pWOZ_r03.png"
   [7] "w0203_s01_pWOZ_r01.png" "w0203_s01_pWOZ_r02.png" "w0203_s01_pWOZ_r03.png"
   [10] "w0238_s01_pWOZ_r01.png" "w0238_s01_pWOZ_r02.png" "w0238_s01_pWOZ_r03.png"
   [13] "w0400_s01_pWOZ_r01.png" "w0400_s01_pWOZ_r02.png" "w0400_s01_pWOZ_r03.png"

4. Ran the following code in RStudio

   main_dir <- "~/Desktop/handwriter_demo"
   model <- fit_model(main_dir = main_dir,
                  model_docs = file.path(main_dir, "data", "model_docs"),
                  num_iters = 200,
                  num_cores = 4,
                  writer_indices = c(1,5),
                  doc_indices = c(7,18))

5. This produces an error: Error in rjags::jags.model(textConnection(model_wrapped_cauchy), data = rjags_data, : RUNTIME ERROR: Unable to resolve the following parameters: docwriter[1] (line 31) docwriter[2] (line 31) docwriter[3] (line 31) docwriter[4] (line 31) docwriter[5] (line 31) docwriter[6] (line 31) docwriter[7] (line 31) docwriter[8] (line 31) docwriter[9] (line 31) docwriter[10] (line 31) docwriter[11] (line 31) docwriter[12] (line 31) docwriter[13] (line 31) docwriter[14] (line 31) docwriter[15] (line 31) letterwriter[1] (line 5) letterwriter[2] (line 5) letterwriter[3] (line 5) letterwriter[4] (line 5) letterwriter[5] (line 5) letterwriter[6] (line 5) letterwriter[7] (line 5) letterwriter[8] (line 5) letterwriter[9] (line 5) letterwriter[10] (line 5) letterwriter[11] (line 5) letterwriter[12] (line 5) letterwriter[13] (line 5) letterwriter[14] (line 5) letterwriter[15] (line 5) letterwriter[16] (line 5) letterwriter[17] (line 5) letterwriter[18] (line 5) letterwriter[19] (line 5) letterwriter[20] (line 5) letterwriter[21] (line 5) letterwriter[22] (line 5) letterwriter[23] (

Expected behavior handwriter should be able to create a model from files where the writer IDs contain letters