Adding a string to the end of a variable then storing it into Y=

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Summary:

A+Str1->X1t

Adding a string to the end of a variable then storing it into Y=

Jon (guest) 06 Feb 2016 16:28

Code:
ClrHome
Func
Plot1(Scatter,L1,L2)
QuartReg L1,L2,Y1
a->A
b->B
c->C
d->D
e->E
"T^4"-> Str1
A+Str1->X1t

What my code is doing is creating a QuartReg equation based off of the data in L1 and L2 then storing the entire function into Y1 so it can be graphed. At the same time a QuartReg equation is made up of 5 parts
a which is #^4
b which is #^3
and so on what my program does is store each one of those numbers as a variable ie a->A
What I want to be able to do is take each part of the equation and add onto the end T^4,T^3,T^2, and T then the last part of the equation wont have a variable.
The reason I want to change the equation from X^4,X^3,X^2, and X is because I want to be able to store the equation into parametric mode to create a parametric mode. The issue I'm having is that when my program gets to:
A+Str1->X1t
I get the error "Data Error"
When I hit GoTo it highlights the STO command aka ->
If you know how to fix this drop a comment or a better way to combine a string and a variable

Re: Adding a string to the end of a variable then storing it into Y=

jonbush 06 Feb 2016 22:01

You cannot use lowercase letters as real variables. Why exactly do you want to convert it to a parametric equation?

Jon (guest) 06 Feb 2016 22:23

@jonbush a parametric equation can be used to track a hurricane by taking the longitude(x) and the latitude(y) putting them into L2 and L3, while L1 is the time, to create a QuartRegression equation that best fits the data you could also use cubic or any other type of equation that is parabolic in shape when graphed. Firt you create an equation based off of the data in L1 and L2 then an equation based off of L1 and L3. Those two equations when entered into parametric mode on the calculator dont autmatically change from X's to T's. In function mode your equations use X while in parametric mode you use T's which stand for time. The lowercase letters are the letters that you get when you create an equations you can access them by going
Vars > Statistics > EQ > there you will see the letters a,b,c,d,and e. On a TI-83 calculator when you use Stat > Calc > any equation. The data is given to you in this form:
QuarticReg
y=ax^4+bx^3+cx^2+dx+e
a = value
b = value
c = value
d = value
e = value

My program takes these lower case letters and store them as variables that can be called in a program A,B,C,D,and E but my question still stands how can I combine a string and a variable?

jonbush 06 Feb 2016 23:57

You have to treat the variable as a string:

"A"+Str1->X1t

Alternately, you can represent your equation using list operations:

sum({A,B,C,D,E}X^{4,3,2,1,0

With this form, you could simply set

"sum({a,b,c,d,e}T^{4,3,2,1,0->X1T

You might also consider parametric splines.

Last edited on 07 Feb 2016 00:00 by jonbush Show more

Jon (guest) 07 Feb 2016 01:33

"A"+Str1->X1t
stores the letter A + str1,
"sum({a,b,c,d,e}T^{4,3,2,1,0->X1T
When I entered this into my program I gotta Data Error that highlighted x1t

jonbush 07 Feb 2016 01:42

That is correct, A will be treated as a variable, and so the value of A will be multiplied by the T^4.

Make sure that you are using the a, b, c, d, e variables from VARS>Statistics…>EQ and the X1T from VARS>Y-VARS>Parametric…

It might be even better to store the coefficients from each regression into a separate list:

/* First regression here */
{a,b,c,d,e->L4
/* Second regression here */
{a,b,c,d,e->L5
//store the parametric equation
"sum(L4T^{4,3,2,1,0->X1T
"sum(L5T^{4,3,2,1,0->Y1T

Last edited on 07 Feb 2016 01:46 by jonbush Show more

Jon (guest) 07 Feb 2016 13:39

The issue with using Sum( is that instead of it storing the equating like aT^4 + bT^3 + cT^2 + d^1 + e. Its returning a value instead of storing it as an equation.
"sum(L4T^{4,3,2,1,0->X1T wont work it gives me a data error highlighting x1t
so I decided to run
disp "sum(L4T^{4,3,2,1,0
and it returned a numerical value instead of an equation

jonbush 08 Feb 2016 00:32

The only way to get it into an equation would be to use number to string conversions. It seems that your end goal is to get a numerical value, so there should be no need for this. I'm not sure why it isn't working for you.