Update vignette

SampleName should be character

vignettes/bistro.Rmd

@@ -68,7 +68,7 @@ Two required, and one optional but often recommended, datasets are required to r
 
 ### Bloodmeal STR profiles (`bloodmeal_profiles`) 
 
-The bloodmeal STR profiles dataset should have one row per allele for each bloodmeal and marker, and include the allele peak height. Homozygous markers should only be included once (i.e. as one row). It must have four columns named SampleName, Marker, Allele, and Height. Here is an example included with `bistro`: 
+The bloodmeal STR profiles dataset should have one row per allele for each bloodmeal and marker, and include the allele peak height. Homozygous markers should only be included once (i.e. as one row). It must have four columns named SampleName, Marker, Allele, and Height. The SampleName column should hold character values. Here is an example included with `bistro`: 
 
 ```{r}
 head(bloodmeal_profiles)
@@ -83,7 +83,7 @@ unique(bloodmeal_profiles$SampleName)
 
 ### Human STR profiles (`human_profiles`) 
 
-The human STR profiles dataset takes a similar format to the bloodmeal STR profiles dataset - it should have one row per allele for each human and marker, but does not require peak heights. Again, homozygous markers should only be included once. The dataset must have three columns named SampleName, Marker, and Allele. Here is an example: 
+The human STR profiles dataset takes a similar format to the bloodmeal STR profiles dataset - it should have one row per allele for each human and marker, but does not require peak heights. Again, homozygous markers should only be included once. The dataset must have three columns named SampleName, Marker, and Allele. The SampleName column should hold character values. Here is an example: 
 
 ```{r}
 head(human_profiles)