Pfthb

So the task is to create a TikZ figure of the CDF of an exponential random variable for three different choices of the rate parameter λ and for x between 0 and 5 (using λ = 0.5, λ = 1 and λ = 1.5). The three different CDF’s should be on the same graph and distinguished by colour. The axes should be labelled.

so far I have:

beginfigure[h!]

centering

begintikzpicture [xscale = 1, yscale=1, domain=0:2]

draw[<->](0,0)--(1,0) node[above]$x$;

draw[<->](0,0)--(0,1) node[right]$y$;

draw[color=green, thick] plot(x,1-exp(-x));

endtikzpicture

captionCaption

labelfig:my_label

endfigure

This is returning error messages saying there are too many closing brackets and I am unsure of where to go from here, as I have tried several different changes and none of them have worked.
Thank you!

This is because mathematical functions with tikz are not written like LaTeX macros. They are written without the reverse bar

All you have to do is write:

draw[color=green, thick] plot(x,1-exp(-x));

documentclass[12pt]article
usepackagetikz

begindocument
begintikzpicture [xscale = 1, yscale=1, domain=0:2]
draw[<->](0,0)--(1,0) node[above]$x$;
draw[<->](0,0)--(0,1) node[right]$y$;
draw[color=green, thick] plot(x,1-exp(-x));
endtikzpicture
enddocument

AndréC already told you what's causing the error. But from your title I am wondering if you are looking for something like the following.

documentclassarticle
usepackagetikz

begindocument
beginfigure[h!]

centering

begintikzpicture [xscale = 1, yscale=1, domain=0:6]
draw[latex-latex](0,2.2) node[left]$y$ |- (6.2,0) node[below]$x$;
foreach X/Col in 0.5/green!60!black,1/blue,2/red
draw[color=Col, thick] plot[variable=x,smooth] (x,1-tanh(X*(3-x)));
endtikzpicture
captionCaption
labelfig:my_label
endfigure
enddocument