do cats purrDo cats purr on purpose or is it involuntary?

I know people say cats purr when they are happy but my cat does it 97% of the time. If I pet her she starts purring, if just walk past her she stops, looks at me and starts purring. If I look at her she stops what she is doing and starts purring. Even when she is sleeping she is purring for a little bit, it is weird.

So is it involuntary or is she just happy? Is that the real reason they even purr?
Both
It was once thought to be involuntary but a recent study shows they can control it.
Cats will purr when they are happy and even sometimes when they are stressed. It sounds to me though like your cat is a very happy go lucky kitty and she's purring because she's happy. :)
listen here's how it goes she purrs she LOVES you because she can be warm nex to you it's just the basic process of cats.
there actually is no real reason for which cats purr because
1 sometimes when i pat my cat it purrs (10-30%)
do cats purr
2 once it was sick and it would not go 2 sleep the only thing it would do was come to the dining room and purr (had to take it to the Veterinarian)

3 sometimes (5-6%) when i gave him a bit of my sausage to eat
It is like smiling. You often smile without consciously thinking, "I'm happy, so I will smile". But that doesn't mean that it's completely involuntary. You can smile on purpose, and you can purposely avoid smiling.

Same thing with purring. You can look at your cat and smile. Your cat can look at you and purr.
One of mine will walk up the the chaise when I'm on it, put his front paws on the cushion and purr to ask permission to jump up. But it can also be a response to stimulus -- good and bad. Purrs are a sign of happiness, but they can also be a sign of pain and several other things. I love the beasty who announces his proximity by purring for my attention -- beatdo cats purrs the heck out of yowling or whining.... and he knows it and that's why he does it. I have one who whines to announce himself and one that makes an "ak ak" noise.... the purr will win every time.
depends on if its a cat or a kitten. kittens purr almost all the time especially a female. i have a female kitten and a male kitten. they both purr alot id say the male purrs 80% of the time and the female 92% of the time and they purr when they are happy. when you look at her that's giving her attention which will make her happy. when u pet her it makes her happy so she will purr. cats live to please you.
It's actually proven that it's a form of communication and self-healing. It stimulates their bones and muscles without using a lot of energy because of the constant frequency coming from their larynx.