Shortcut for delete in mac

Shortcut for delete in mac

command + delete.

differences between t test and z test

                distribution                                            sample size      variance known or unknown
t test       normally distributed                                can be small      unknown
z test      no requirements for normality b/c clt      is large              known

Odds and odds ratio in statistics

https://stats.idre.ucla.edu/other/mult-pkg/faq/general/faq-how-do-i-interpret-odds-ratios-in-logistic-regression/

The odds of success are defined as the ratio of the probability of success over the probability of failure



confidence interval

https://ncss-wpengine.netdna-ssl.com/wp-content/themes/ncss/pdf/Procedures/PASS/Confidence_Intervals_for_the_Odds_Ratio_in_Logistic_Regression_with_One_Binary_X.pdf

Assumptions of linear models

https://www.theanalysisfactor.com/assumptions-of-linear-models/

1. The residuals are independent
2. The residuals are normally distributed
3. The residuals have a mean of 0 at all values of X
4. The residuals have constant variance

Data science interview questions

http://alexbraunstein.com/2011/08/09/hire-data-scientist-statistician/



https://www.datasciencecentral.com/profiles/blogs/66-job-interview-questions-for-data-scientists

Apply, sapply, tapply differences in R

https://www.guru99.com/r-apply-sapply-tapply.html

Apply: on matrice

apply(mat,1,var)


1: row,  margin
2:column, margin


lapply: apply on a vector, return a list, no margin

movies <- c("SPYDERMAN","BATMAN","VERTIGO","CHINATOWN")
movies_lower <-lapply(movies, tolower)
[[1]]
[1] "spyderman"
[[2]]
[1]"batman"
...

sapply does the same job as lapply, but return a vector


tapply computes a measure ( min, max, median etc) or a function for each factor variable in a vector.

data(iris)

tapply(iris$Sepal.Width, iris$Species, median)

https://www.r-bloggers.com/using-apply-sapply-lapply-in-r/

How to use ftp on the linux shell

https://www.howtoforge.com/tutorial/how-to-use-ftp-on-the-linux-shell/


https://blog.eduonix.com/shell-scripting/how-to-automate-ftp-transfers-in-linux-shell-scripting/

Good and concise naive bayes classifier sentiment analysis tutorial on youtube.

https://www.youtube.com/watch?v=0kTUXhsdhtY

Github tutorial

Github tutorial

https://www.youtube.com/watch?v=0fKg7e37bQE

pyspark tutorial

pyspark tutorial


https://www.dezyre.com/apache-spark-tutorial/pyspark-tutorial

https://www.tutorialspoint.com/pyspark/index.htm

Non-normal distributions and their applications.

https://www.utdallas.edu/~scniu/OPRE-6301/documents/Important_Probability_Distributions.pdf


Binomial
Poisson
Uniform
Normal
 Exponential

https://mathcs.clarku.edu/~djoyce/ma218/distributions.pdf

Generate a cookie python

Generate a cookie python

http://infohost.nmt.edu/tcc/demo/pycgi/pycgi.pdf

A good youtube math and machine learning channel

Here is a good youtube math and machine learning channel.

https://www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw

And it has a video series, machine learning Neural network for recognizing numbers

https://www.youtube.com/watch?v=aircAruvnKk

Randomly generate user agents and ip in python

1. randomly generate user agent

installation:
pip install fake_useragent

usage:

from fake_useragent import UserAgent

ua=UserAgent()

ua.random

got a random user agent


2. randomly generate ip

'.'.join('%s'%random.randint(0, 255) for i in range(4))

machine learning questions.

neural network

https://www.cs.toronto.edu/~tijmen/csc321/slides/lecture_slides_lec1.pdf

supervised and unsupervised learning

https://machinelearningmastery.com/supervised-and-unsupervised-machine-learning-algorithms/

How to send emails on linux.

I use ubuntu system. How to find out which system you use, command is "uname -a".

I tried to send out email on ubuntu.

I tried on command line first.

I first installed postfix:

sudo apt-get install postfix

Then I tried the command:

echo "test message" | mailx -s "test subject" XXXX@xxx.com

And I got the following:

The program 'mailx' is currently not installed. You can install it by typing:

sudo apt-get install mailutils

So I installed mailx.

I got the message. 

And I put it in a linux shell script. Got it done. 

How to prevent your scrapy from being banned.

How to prevent your scrapy from being banned.

https://www.cnblogs.com/rwxwsblog/p/4575894.html