Elementary Mathematics, Part 1 gives the following guidelines:
Because a line plot is based on a number line, it must be drawn for grades K-3. The values appear below the horizontal line, without the numeric indicator. The first digit of the value is aligned with the scale mark. Arrows are on either end of the horizontal line as in print. The label of the line plot is aligned with the first cell of the number line with no blank line between. X's are not drawn. They are represented by the full cell.
I would highly encourage anyone brailling elementary mathematics to get copies of the workshop materials "Elementary Mathematics, Part 1" and "Elementary Mathematics Part 2" from the Professional Development Conference, April 3-5, 2008, Dallas, Texas. They cover almost everything you will find in elementary math texts with examples of the braille and the tactile drawings.
It is also important to note that a transcriber's note should be inserted explaining the change from the print X'x to the use of the full cell in braille. If you haven't had a chance to check it out yet, the on-line version of Guidelines and Standards for Tactile Graphics has been posted on the BANA website. In the math section, Unit 6, line plots are discussed and an example is also included.
Because a line plot is built on a number line, you need to follow the rules for number lines discussed earlier in the document. In Unit 6, 188.8.131.52 For kindergarten through grade 3, it says:
"The number line must be shown as a tactile graphic. The axis line, coordinate marker, and line segments should be raised tactile lines; only the labels should be brailled."
So yes, as Crepe Myretle also indicated, it must be [u]drawn[/u] for grades K-3. That is, the number line will have to be done as tactile lines rather than braille cells. Hope this clarifies things for you ...