Error using input Unrecognized function or variable 't'.

Hi everyone, can you help me fix this problem

***This is my matlab code

clear all
clc

prompt1='Her retirement increases by R1 % per year  ';
prompt2='Plus R2 % of her yearsalary ';
prompt3='Time she started working ';
prompt4='Her salary S(t) increase exponentially after t years';
R1= input(prompt1);
R2= input(prompt2);
p= input(prompt3);
S= input(prompt4);

syms A(t) 
ode = diff(A,t) -R1*A == R2*S;
cond = A(0) == 0;
ASol(t) = dsolve(ode,cond);
ASol(p)

***And when i put number and run

Her retirement increases by R1 % per year  
0.06
Plus R2 % of her yearsalary 
0.12
Time she started working 
40
Her salary S(t) increase exponentially after t years
30*exp(t/20)
Error using input
Unrecognized function or variable 't'.

Error in untit5led (line 11)
S= input(prompt4);
 
Her salary S(t) increase exponentially after t years

***Thank you very much.

Answer 1

[Walter Roberson]

S= input(prompt4);
syms A(t) 

Notice you have the input(prompt4) call before you have the syms A(t) call. Because of that order, the symbolic variable t has not been defined yet, and so is not available for when the user types in 30*exp(t/20) in response to the input() prompt.

You need to move the syms line to before the S= line.