TI-Basic: How do you get an equation as an input?

Question

I was playing around with programming on my TI-84 in math class today and I decide to try to write a program that reads an equation and than does a few things with it. But I'm having trouble reading an equation. I tried :Prompt Y1 but I kept getting a data type error when I try to use the program. Does anyone have any ideas on how to accomplish this? Thanks in advance.

Answer 1

I'm not sure if the TI-84 is the same, but on the 83 this will work if you put the equation in quotes when you enter it. So for example, using the following program:

PROGRAM:TEST
:Prompt Y1
:ClrDraw
:DispGraph

Running it:

prgmTEST
Y1=?"2X+1"

Will cause the graph for y=2x+1 to be drawn (and any other equations you already had entered at the time, IIRC).

Answer 2

Alternatively, you can do

:Input "Eqn:",Str1
:String>Equ(Str1,Y1)
:DispGraph

This way you don't have to put in quotation marks each time you enter an equation.

As noted by Timtech, there is an easier way of writing this.

:String►Equ(Str1,Y1
can be
:Str1→Y1

This replacement is universal, takes the same time to run (because it actually uses the same routines), is more convenient to type since you don't have to go through the command catalog, and is two bytes smaller.

Excerpt from the TI-Basic Developer Information Repository.

Answer 3

Texas Instruments has guide books online for some of their programmable calculators. Here's the PDF for the TI-84 plus: http://education.ti.com/guidebooks/graphing/84p/TI84PlusGuidebook_Part2_EN.pdf. Check out chapter 16 on programming.