# Check table value

I am hopelessly lost in all of this, but I feel like there should be a way to do what I want…

Here’s my Work In Progress: https://teacher.desmos.com/activitybuilder/custom/5e9f5198762da1796f45598e

I would like to check if the values students enter into the table on the last screen really are solutions to the system of equations and have a check mark appear in the dashboard.

I created a c_orrect number in the first graph, then copied that graph through. My hope is that I can use the values in the table to set numbers “a” and “b” in graph1 (screen 9), then on screen 12, I can check to see if “a” and “b” set the value of c_orrect to 1. Ultimately, I would use all of the inequalities, but I’m just testing with the first one. I would then hide all of that work and not display those lines.

Is this the right approach? Can it be tweaked to work?

Thanks in advance!

Try checking out some of this thread…

I have used a template posted for checking values in a table. Every example has integer values assigned to the answer variable. How do I assign an irrational number or for that matter a negative fraction to the answer checking cell?

You mean the parameters in evaluateAt() if I’m understanding correctly. You can use numericValue to directly calculate something as a parameter. You can also use variables you create, which is less messy. Just be careful with irrational and non-terminating variables. You’ll always want to round. Say I already had an equation in terms of x, eq1 and I want to evaluate for pi:
n = eq1.evaluateAt(numericValue("\pi"))
or

pi=numericValue("\pi")
n = eq1.evaluateAt(pi)


or a negative fraction:
n = eq1.evaluateAt(numericValue("-2/3"))
or

myFraction = numericValue("-2/3")
n = eq1.evaluateAt(myFraction)


See this other recent thread about comparing values.

Thanks but what I want to do is check whether an irrational number value entered by a student in a table is the correct answer. For instance in the code you posted for “table based automatic checking” your example checks answer1=1. I want to check: answer= \sqrt(2)/2

Right. What I was trying to get across was to use numericValue if you need non-integer.

answer = numericValue("\sqrt(2)/2")

But just recognize with non-terminating decimals comparisons do not always work cleanly and you’ll want to do something similar to the other thread I referenced. Like this anwer rounded to 4 decimal places would be better for comparison:
answer = numericValue("\round(\sqrt(2)/2, 4)")

(In my original response to you replace the pi or myFraction with answer.)

Ahh, got it…thanks so much

I tried your rounding hack (4 decimal places) but when I enter the symbolic representation in the answer field it is not comparing correctly.

Oh, you’ll want to compare to the cell value rounded as well so something like:

answer = numericValue("\round(\sqrt(2)/2, 4)")
student = numericValue("\round(\${this.cellContent(1,2)}, 4)")
correct= answer = student


where answer is the target answer and student is the student’s input in row 1 column 2, each rounded to 4 decimal places. correct outputs true or false for whether answer=student.

The rounding seems like extra, but comparing unrounded decimals can lead to errors. I’m not a developer so I can’t precisely explain why.

That makes perfect sense but I still can’t get it to work. Would you have a look at my code? The offending screen is #9.

Looks like answer5 and answer6 were coming up undefined. I put -sqrt2/2 into the desmos calculator, then copy/pasted into CL and this works as a replacement:

answer5 = numericValue("\round(-\frac{\sqrt{2}}{2}, 4)")

Parentheses instead of curly braces for sqrt was probably the main culprit.

Also, I might suggest using cellSuffix to give feedback for each individual cells instead of trying to conditionally change your note so much. Here’s my version. I also used countNumberUsage to ensure students are typing the radical.

Excellent! thanks, one last question. How would I check for an answer “undefined”

You could use isUndefined().

check1= isUndefined(this.cellNumericValue(1,2))

(I didn’t try it, but something to that effect.)

Great, that does exactly what I want.