Lecture 1 - Software for Statistics

Question 1

Central Processing Unit

Answer 1

Controls the computer and executes instructions

Question 2

Different types of memory

Answer 2

Registers - within the CPU, superfast
Random Access Memory - slower
Mass storage - hard disk drives etc, much slower

Question 3

How are programming languages classified ?

Answer 3

Level of abstraction (low/high)
Speed/Efficiency
Generality
Generations

Question 4

What is difference between low level and high level language?

Answer 4

Low level - close to specific hardware

High level - far from the hardware, closer to natural language

Question 5

What type of language (lower/higher) is faster?

Answer 5

Lower languages tend to be faster but this is not always true

Question 6

1st Generation

Answer 6

Machine language - CPU specific set of instructions.

Relatively few instructions and many of these required to achieve anything useful

Question 7

2nd Generation

Answer 7

Assembly language

Human readable version of machine language

Question 8

3rd Generation

Answer 8

More human friendly, CPU independent language with variables, data, and code structures.
Also object oriented languages such as C++ and Java.

Question 9

4th Generation

Answer 9

Language designed with a specific application in mind.
Lots of built in capabilities for that application.
Database query languages (SQL), graphical user interface creators, mathematics languages, statistic languages.

Question 10

5th Generation

Answer 10

Language based on solving problems given the problem specifications.
User does not need to explicitly write the algorithm for solving the problem

Question 11

Interpreted Language

Answer 11

Turns each line into machine code as it is entered using an interpreter and run it straight away.

Question 12

Compiled Language

Answer 12

Once code is written and saved into a file, turn it all into machine code in one go using a compiler. Then it can be run.

Question 13

Difference between Interpreted and Compiled coding languages

Answer 13

Interpreted codes provides instant feedback - good for run once short jobs. Tend to be used by 4GL.
Compiled code runs faster - good for jobs that will run many times. Tend to be used by 3GL

Question 14

What programming language for stats?

Answer 14

For simple run once stuff - favourite stats package. (CON: no reproducile trail)
More complex stuff to be run once or few times - 4GL with an interpreter
Production software or where efficiency is important - 3GL and compile or prototype in 4GL then rewrite the slow bits in 3GL.

Question 15

Software for enormous data sets

Answer 15

SAS/ Microsoft R open/ R with Hadoop

Question 16

Pros and Cons of R

Answer 16

Pros:
Contains cutting edge methods
Highly extensible
Free

Cons:
Steep learning curve
Less well supported than a commercial package
Greater tendency to ignore backwards computability.

Question 17

What is an algorithm?

Answer 17

An ordered sequence of unambiguous and well defined instructions for performing some task and halting in finite time

Question 18

Important features of an algorithm

Answer 18

An ordered sequence
Unambiguous and well defined instructions, each instruction is clear, do-able, and can be done without difficulty
Performs some task algorithm needs to be complete, with nothing left out
Halts in finite time

Question 19

Phase 1 of an R programmer

Answer 19

R as a calculator

Question 20

Phase 2 of an R programmer

Answer 20

The script
10-15 lines of code strung together to perform a task
Might have a loop, maybe even an if statement.
One or two comments
Not intended for the use of others

Question 21

Phase 3 of an R programmer

Answer 21

Modular programming with functions
Undertaking a sufficiently complex analysis that organisation becomes critical
Description of input and outputs are critical to ensure reusability
When performing functional programming there are elements of R language that become useful (e.g. stop( ) )