Sometimes you want to exclude some specific rows of data in your dataset. This might be because:
- There is something wrong with the data (you can see from the values that it's been typed in wrong, like if a person's height was set to 12 feet, but you don't know what the right value should have been).
- You want to show just a subset of your data on the graph (you collected data from three classes, but only want to show for two of them)
How do I do it?
In the TABLE tab, click the Excluded checkbox at the end of each row:

Excluding many rows with similar values
Three options to exclude:

Use a Filter to set the exclude checkboxes dependent on the contents of one or more columns. See this article for details.

Exclude by value of a Categorical column. Open the gear icon for the column and use the Exclude tools there. Read more specifics here.

Select all the rows in a range (drag down the left row# column to select the rows, or click on the first row and then shift-click on the final row) and then click any Exclude checkbox in the range to exclude or de-exclude them all at once.