# CS代考程序代写 LECTURE 2 TERM 2:

LECTURE 2 TERM 2:
MSIN0097
Predictive Analytics Video 5: Classification
A P MOORE

CL ASSIFIC ATION
A. ClAssification B. Regression
C. Clustering D. Decomposition
Supervised
Unsuper vised

A. CLASSIFICATION CATEGORICAL VARIABLE

A. CLASSIFICATION CATEGORICAL VARIABLE

A. CLASSIFICATION CATEGORICAL VARIABLE

A. CLASSIFICATION CATEGORICAL VARIABLE

GRID (PIXEL) DATA

VARIATION IN DIGITS

PARTITIONING DATA

K-FOLD VALIDATION

CONFUSION MATRIX BINARY FORCED CHOICE
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A. CLASSIFICATION CATEGORICAL VARIABLE
Model 1
predicted
predicted
Model 2
actual
actual

CONFUSION MATRIX

SINGLE METRICS
𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 = 𝑅𝑒𝑐𝑎𝑙𝑙 =
𝐹1 =
𝑇𝑃
𝑇𝑃 + 𝐹𝑃 𝑇𝑃
𝑇𝑃 + 𝐹𝑁 2
=2×𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛×𝑅𝑒𝑐𝑎𝑙𝑙= 𝑃𝑟𝑒𝑐𝑖𝑖𝑠𝑜𝑛 + 𝑅𝑒𝑐𝑎𝑙𝑙
𝑇𝑃
𝑇𝑃 + 𝐹𝑁 + 𝐹𝑃 2
1
𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 𝑅𝑒𝑐𝑎𝑙𝑙
+
1

SENSITIVITY, SPECIFICITY…
https://en.wikipedia.org/wiki/Confusion_matrix
Prevalence
Accuracy
Positive predictive value False discovery rate False omission rate Diagnostic odds ratio…

PRECISION / RECALL TRADE OFF
Decision function

DECISION THRESHOLD

PR CURVE

ROC CURVE & AUC
https://en.wikipedia.org/wiki/Confusion_matrix

AUC – MODEL SELECTION

BINARY CLASSIFICATION

MULTICL ASS

MULTICL ASS
— one-versus-the-rest (OvR) strategy (also called one-versus-all) — one-versus-one (OvO) strategy

CONFUSION MATRIX

CONFUSION IMAGE

CONFUSION ERRORS

CONFUSION ERRORS

ANALYZING ERRORS 3 VS 5
TP1 0FN 1
0
FP TN

FAILURE MODES – GENERALIZATION

CL ASSIFIC ATION
— Multilabel Classification
— Multioutput Classification

DENOISING

DENOISING

REVIEW
— Select good metrics for classification tasks
— How to pick the appropriate precision/recall trade-off
— How to compare classifiers
— Different classification systems for a variety of tasks
— What business problems can you think of that are classification tasks?
— Can you think of some business problems that are multilable and multioutput?

TEACHING TEAM
Dr Alastair Moore Senior Teaching Fellow
a.p.moore@ucl.ac.uk
@latticecut
Kamil Tylinski Teaching Assistant
kamil.tylinski.16@ucl.ac.uk
Jiangbo Shangguan Teaching Assistant
j.shangguan.17@ucl.ac.uk