# How to show the variable name instead of its value in a plot's text, when using "syms", "text" and "latex" functions

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Sim on 26 Aug 2022
Commented: Sim on 28 Aug 2022
Question: By using both syms, latex and text functions/tools (as in the example here below), how can I show the variable name instead of its value, in a plot's text ?
What I currently have: In this example, if I assign a value to the variable "a", i.e. "a = 0.01", the latex function will show its value, i.e. "0.01" (i.e. "1/100") and not its name, i.e. "a".
syms x
a = 0.01 ;
y = exp(-a*x); % equation to show inside the plot
figure
fplot(y, [0 500])
text(100,0.5, ['\$y = ' latex(y) '\$'], 'Interpreter','latex', 'FontSize',16) My desired output: If possible, I would like to still use both syms, latex and text functions/tools (as in my example), and see/show the variable name "a" in the plot's text, instead of its value "0.01" (i.e. "1/100"). Dyuman Joshi on 26 Aug 2022
syms y(a,x)
y(a,x) = exp(-a*x); % equation to show inside the plot
figure
fplot(y(0.01,x), [0 500])
text(100,0.5, ['\$y = ' latex(y) '\$'], 'Interpreter','latex', 'FontSize',16) Sim on 28 Aug 2022
thanks a lot @Dyuman Joshi!!

Walter Roberson on 26 Aug 2022
You cannot do that, not without reconstructing the formula
syms x
a = 0.01 ;
y = exp(-a*x); % equation to show inside the plot
children(y)
ans = 1×1 cell array
{[-x/100]}
children(ans{1})
ans = 1×2 cell array
{[x]} {[-1/100]}
Notice that there is no "a" anywhere in the breakout of the expression.
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Sim on 28 Aug 2022
thanks @Walter Roberson! ....but..... what do you think about the @Dyuman Joshi solution ?
It looks like working for my needs.... I mean, in that wasy I do not need to write the equation more than once....