# Logistic Regression with a Neural Network mindset

Welcome to your first (required) programming assignment! You will build a logistic regression classifier to recognize cats. This assignment will step you through how to do this with a Neural Network mindset, and so will also hone your intuitions about deep learning.
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## (Neural Network) Derivative of sigmoid function $f(z)=\frac{1}{1+e^{-z}}$ $f'(z)=f(z)(1-f(z))$

Process:

$$f(z)=\frac{1}{1+e^{-z}}$$
$$f'(z)=\frac{e^{-z}}{{(1+e^{-z}})^{2}}$$
$$=\frac{1+e^{-z}-1}{{(1+e^{-z}})^{2}}$$
$$=\frac{1}{(1+e^{-z}}) – \frac{1}{{(1+e^{-z}})^{2}}$$
$$=y(1 – y)$$

## JVM: Stack VS. Heap VS. Method Area Similar to Operating System, Java Virtual Machine offers a runtime data area. This time, I make a summery about stack, hep and method.

## Why we said JAVA is Pass by Value

Today, I was asked a question that Does Java pass by reference or pass by value?

A popular mistake is that when we pass primitives like int, char, etc. it pass by value, and when we pass objects, it pass by reference.

## NameError: name ‘urllib2’ is not defined

I am studying mongoDB with python, I met this problem.

When I tried to open a url by python, I copied some code from internet like following:

and met this error:
NameError: name urllib2 is not defined

Then I found that ‘urllib2’ is a lib for python2 while I use python3

Solution is easy by changing import lib

With this url, you can get two month free trial with a \$300 credit for one year.

## (crawler4j)SLF4J: Failed to load class “org.slf4j.impl.StaticLoggerBinder”.

While using crawler4j to crawl some data, I met errors as following:

Based on the official document I found solution:

https://www.slf4j.org/codes.html#StaticLoggerBinder

Then I downloadedlogback and import logback-classic.jar.

Perfect!

## Azure Function Error: The resource you are looking for has been removed, had its name changed, or is temporarily unavailable.

These days, I changed one of my Node.js Application from AWS to Azure. However, some functions do not work after migrating. http://quickstart.cloudera:19888/jobhistory