# 1.4 Machine learning lecture 5  (Page 13/15)

And so having estimated all these parameters, when you’re given a new piece of email that you want to classify, you can then compute PFY given X using Bayes rule, right? Same as before because together these parameters gives you a model for PFX given Y and for PFY, and by using Bayes rule, given these two terms, you can compute PFX given Y, and there’s your spam classifier, okay? Turns out we need one more elaboration to this idea, but let me check if there are questions about this so far.

Student: So does this model depend on the number of inputs?

Instructor (Andrew Ng) :What do you mean, number of inputs, the number of features?

Student: No, number of samples.

Instructor (Andrew Ng) :Well, N is the number of training examples, so this given M training examples, this is the formula for the maximum likelihood estimate of the parameters, right? So other questions, does it make sense? Or M is the number of training examples, so when you have M training examples, you plug them into this formula, and that’s how you compute the maximum likelihood estimates.

Student: Is training examples you mean M is the number of emails?

Instructor (Andrew Ng) :Yeah, right. So, right. So it’s, kind of, your training set. I would go through all the email I’ve gotten in the last two months and label them as spam or not spam, and so you have – I don’t know, like, a few hundred emails labeled as spam or not spam, and that will comprise your training sets for X1 and Y1 through XM, YM, where X is one of those vectors representing which words appeared in the email and Y is 0, 1 depending on whether they equal spam or not spam, okay?

Student: So you are saying that this model depends on the number of examples, but the last model doesn’t depend on the models, but your phi is the same for either one.

Instructor (Andrew Ng) :They’re different things, right? There’s the model which is – the modeling assumptions aren’t made very well. I’m assuming that – I’m making the Naive Bayes assumption. So the probabilistic model is an assumption on the joint distribution of X and Y. That’s what the model is, and then I’m given a fixed number of training examples. I’m given M training examples, and then it’s, like, after I’m given the training sets, I’ll then go in to write the maximum likelihood estimate of the parameters, right? So that’s, sort of, maybe we should take that offline for – yeah, ask a question?

Student: Then how would you do this, like, if this [inaudible] didn’t work?

Instructor (Andrew Ng) :Say that again.

Student: How would you do it, say, like the 50,000 words –

Instructor (Andrew Ng) :Oh, okay. How to do this with the 50,000 words, yeah. So it turns out this is, sort of, a very practical question, really. How do I count this list of words? One common way to do this is to actually find some way to count a list of words, like go through all your emails, go through all the – in practice, one common way to count a list of words is to just take all the words that appear in your training set.

That’s one fairly common way to do it, or if that turns out to be too many words, you can take all words that appear at least three times in your training set. So words that you didn’t even see three times in the emails you got in the last two months, you discard. So those are – I was talking about going through a dictionary, which is a nice way of thinking about it, but in practice, you might go through your training set and then just take the union of all the words that appear in it.

find the 15th term of the geometric sequince whose first is 18 and last term of 387
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
can someone help me with some logarithmic and exponential equations.
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
a perfect square v²+2v+_
kkk nice
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
rolling four fair dice and getting an even number an all four dice
Kristine 2*2*2=8
Differences Between Laspeyres and Paasche Indices
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
how do you translate this in Algebraic Expressions
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!