Checking cell content that includes more than one variable

Questions
1

On the screen below, I am hoping to add a column to check the correctness of the equations that students type in. Is there a way to do this in a table, even though there is no latex source? I had thought about using the evaluateAt function, but I don’t think that I can since there are variables on both sides of the equal sign.

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2

By default, each column in a table is set to ‘Format as math’, and this means that when you use something like this.cellContent(1,2) you are automatically getting the Latex value of a student’s input. This opens up a few ways to add correctness checks depending on how thorough and complex you want to get:

  1. You could check the exact Latex string a student enters, but then you run the risk of marking some correct answers as incorrect based on format choices (e.g. a student enters 0.5 instead of 1/2 or they enter y - -4 instead of y + 4).

  2. You can turn each equation into an xyLine and check its slope and y-intercept. This is a great way of checking that a student entered some correct equation, but it doesn’t differentiate between point-slope and slope-intercept formats for writing equations. This would look like
    line12 = xyLine(this.cellContent(1,2))
    correct: (line12.slope = 0.5) and (line12.yIntercept = -4.5)

  3. You could build off #2 and add an additional check on just the left-hand side of the equation to differentiate between point-slope and slope-intercept equations. This gets tedious when you have lots of equations to check on the same screen, but it would look like
    line12 = xyLine(this.cellContent(1,2))
    lhs12 = simpleFunction(parseEquation(this.cellContent(1,2)).lhs, "y")
    correct: (line12.slope = 0.5) and (line12.yIntercept = -4.5) and (lhs12.evaluateAt(0) = 4)

So, the functionality to do what you want is definitely there :slight_smile: Other folks, please chime in if you have alternative, more elegant solutions. Good luck!

3

Thank you so much! This was very helpful! In case anyone else wants to see the finalized code, here is the check that I wrote for each line:

#Row 1:
line1a=xyLine(Table10.cellContent(1,2))
line1b=xyLine(Table10.cellContent(1,3))
cellContent(1,4): when line1a.slope=0.5 and line1b.slope=0.5 and line1a.yIntercept=-4.5 and line1b.yIntercept=-4.5 “:heavy_check_mark:” otherwise “:x:”