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I regularly take down notes and paste them on the shields of my desk. When the shields are full, I remove some and transcribe the contents here.

### 04-09-2017

• The graphical model captures the causal process by which the observed data was generated. For this reason, such models are called generative models.
• Explain away: to dismiss or minimise the significance of something by explanation.
• clique: a small close-knit group of people who do not readily allow others to join them.
• Interquartile range (IQR) = middle 50% = Q3 - Q1
• Point beyond 1.5IQR mild outlier
• Point beyond 3IQR extreme outlier
• 联合熵 joint entropy H(X,Y) = - sum_x sum_y p(x,y)logp(x,y)
• H(X,Y) >= max{H(X),H(Y)}
• H(X,Y) ⇐ H(X) + H(Y)
• H(X,Y) = H(X) + H(Y) if X and Y are independent.
• H(Y|X) = H(X,Y) - H(X)
• Conditional entropy 条件熵
• H(Y|X) entropy of Y conditioned on X
• H(Y|X) = sum_x p(x) H(Y|X=x) = - sum_x,y p(x,y)logp(y|x)
• H(Y|X) = 0 if Y completely determined by X
• H(Y|X) = H(Y) if Y,X are independent
• Mutual information 互信息
• I(X;Y) = H(X) - H(X|Y) = H(Y) - H(Y|X) = H(X) + H(Y) - H(X,Y) = H(X,Y) - H(X|Y) - H(Y|X)
• I(X;Y) = D_KL(p(x,y)||p(x)p(y))
• Gini(X) = 1 - sum p_i^2
• Entropy H(X) = -sum p_i logp_i
• 两者均衡量不确定性，趋势相同，Gini加1保证非负
• H(Y|X) = H(X|Y) + H(Y) - H(X) ←- Bayes' rule
• H(Y|X) ⇐ H(Y)
• H(X,Y) = H(X|Y) + H(Y|X) + I(X;Y)
• H(X,Y) = H(X) + H(Y) - I(X;Y)
• I(X;Y) ⇐ H(X)
• from sklearn.model_selection import train_test_split
• from sklearn.model_selection import cross_val_score
• K-Folds Cross Validation
• Leave One Out Cross Validation
• inherent conflict: degeneracy of the covariance function is good for computational reasons, but bad for modelling reasons.
• VIM 快捷键
• ctrl+d: page down
• ctrl+u: page up
• *: next occurance
• #: prev occurance
• \+: at least once
• shift+Enter 五笔
• dfu-util -a 0 –dfuse-address 0x08000000 -D x.bin

### 03-08-2017

• logit: logistic probit, coined by J. Berkson in 1944, inverse of logistic function.
• odds: p/(1-p)
• quantile function: inverse of CDF
• Beta distribution: support x\in[0,1], f(x) = 1/B(a,b)*x^(a-1)(1-x)^(b-1)
• E[x] = a/(a+b)
• suitable for random behaviour of percentages and proportions.
• Binary Search Tree: left subtree smaller, right subtree bigger.
• Gini impurity: (G as in Gene) I_G = sum_{i=1}^m p_i(1-p_i) = 1 - \sum p_i^2
• docker exec -it ID bash, run a command (bash) in a running container
• docker run -it image, run a command in a new container, RUN instead of EXEC
• docker ps -l, list containers
• docker commit containerID, create a new image from container's change
• docker run -e DISPLAY=192.168.xx.xx:0 -v /tmp/.X11-unix:/tmp/.X11-unix:rw osrf/ros:kinetic-desktop rqt
• docker images
• docker search
• numpy matrix multiplication, a.dot(b)
• element-wise multiplication, a*b
• comma indicates a tuple should be constructed
• hostname -i, show IP address

### 12-07-2017

• 假设属性之间相互独立
• Naive Bayes, x = [x_1, \ldots, x_n] feature vector, C_k: class k, p(C_k|x) \prop p(x|C_k)p(C_k).
• By assuming each feature is conditionally independent of every other one given class C_k, then p(x|C_k) = \prod p(x_i|C_k).
• :v/pattern/p, vim find lines not matching a pattern
• sudo iptables -L -n, display firewall status
• which, whereis, locate programs
• NP-Hardness: non-deterministic polynomial-time hard, i.e. at least as hard as the hardest problems in NP.
• ReLU: Rectified linear unit
• if the posterior distribution p(\theta|x) is in the same family as the prior distribution, then the prior and posterior are called conjugate distributions, and the prior is called the conjugate prior for the likelihood function.

### 25-04-2017

• DELETE FROM table WHERE id BETWEEN 10 and 200
• mount -o remount, rw /
• mount -o remount, ro /
• X band, 8-12GHz, 3.75-2.5cm
• sudo dd bs=4M if=/dev/sdb | gzip > pathtoimage.gz
• gzip -dc pathtoimage.gz | sudo dd bs=4M of=/dev/sdb
• sudo dd bs=4M if=/dev/sdb | gzip > pathtoimage.gz
• gzip -dc pathtoimage.gz | sudo dd bs=4M of=/dev/sdb
 git remote -v
git remote add upstream https:// ....git
git fetch upstream
git checkout master
git merge upstream/master
git push origin master
• COMMAND_LONG(#76)
• COMMAND_INT(#75)
• heter- other alter
• laser pulse time-of-flight(TOF)
• AP6212 = STM32F205 + BCM43438, 2MB Flash

### 08-09-2015

• 2693451744
• ss -aut4
• ip.src == 192.168.1.130 and http
• OPPORTUNIST: A person who exploits circumstances to gain immediate advantage rather than being guided by consistent principles or plans.

Use OpenBUGS in R

library(BRugs)
writeLines(modelString,con="model.txt")
modelCheck( "model.txt" )
modelData(bugsData(list))
modelCompile()
modelGenInits() or ModelInits(bugsInits(initfunc()))
samplesSet(c("",""))
modelUpdate(burnin)
samplesSample("")
samplesStats("")

top

• a - PID
• c - absolute path
• P - CPU
• M - memory

Two modifications of the PIXHAWK code

1. /src/modules/px4iofirmware/safety.c safety_button_pressed = 1
2. commander.c line 1338 if updated safety.safety_switch_available = false
set root=(hd0,7)
linux /vmlinuz-linux root=/dev/sda5
initrd /boot /initramfs-linux.img
boot