Use write.csv() only on data's head()

episodes/11-supp-read-write-csv.Rmd

@@ -247,10 +247,10 @@ read.csv(
 After altering our cars dataset by replacing 'Blue' with 'Green' in the `$Color` column, we now want to save the output. There are several arguments for the `write.csv(...)` [function call](../learners/reference.md#function-call), a few of which are particularly important for how the data are exported.  Let's explore these now.
 
 ```{r writeData}
-# Export the data. The write.csv() function requires a minimum of two
-# arguments, the data to be saved and the name of the output file.
+# Export the first rows of data. The write.csv() function requires a minimum of
+# two arguments, the data to be saved and the name of the output file.
 
-write.csv(carSpeeds, file = 'data/car-speeds-cleaned.csv')
+write.csv(head(carSpeeds), file = 'data/car-speeds-cleaned.csv')
 ```
 
 If you open the file, you'll see that it has header names, because the data had headers within R, but that there are numbers in the first column.
@@ -263,7 +263,7 @@ If you open the file, you'll see that it has header names, because the data had
 This argument allows us to set the names of the rows in the output data file. R's default for this argument is `TRUE`, and since it does not know what else to name the rows for the cars data set, it resorts to using row numbers. To correct this, we can set `row.names` to `FALSE`:
 
 ```{r row.namesFALSE}
-write.csv(carSpeeds, file = 'data/car-speeds-cleaned.csv', row.names = FALSE)
+write.csv(head(carSpeeds), file = 'data/car-speeds-cleaned.csv', row.names = FALSE)
 ```
 
 Now we see:
@@ -300,7 +300,7 @@ Now we'll set `NA` to -9999 when we write the new .csv file:
 
 ```{r naUserSelected}
 # Note - the na argument requires a string input
-write.csv(carSpeeds,
+write.csv(head(carSpeeds),
           file = 'data/car-speeds-cleaned.csv',
           row.names = FALSE,
           na = '-9999')