Calculators

pari/gp | mathics | excel | r | hp-11c

bc | shell | browser | emacs | postgresql | glpsol

What are the best calculators?

pari/gp

pari/gp compared

Install and run gp:

$ brew install pari
$ gp
? (2/7)^20
%1 = 1048576/79792266297612001
? %1 * 1.
%2 = 1.3141323697825355135314451523953967139 E-11

The value for each expression evaluated is stored in a variable with a leading percent sign. Integers and rational numbers are arbitrary length. Multiply by 1. or add 0. to get a decimal approximation.

The number of digits in a decimal approximation can be set to an arbitrarily large value. To see the first 100,000 digits of π:

? \p 100000
? Pi

Use ? to get online help, and ?\ to get a description of the "keyboard shortcuts", which are commands which start with a backslash.

gp has complex numbers. The real and imaginary parts can be rationals or decimal approximations:

? real(1 + 3 * I)
%3 = 1
? imag(1 + 3 * I)
%4 = 3
? abs(1 + 3 * I)
%5 = 3.1622776601683793319988935444327185337
? arg(1 + 3 * I)
%6 = 1.2490457723982544258299170772810901231

There are matrices and vectors:

? [1,2;3,4] * [4,3;2,1]
%1 = 
[ 8  5]

[20 13]

? [1,2;3,4]~
%2 = 
[1 3]

[2 4]

? [1,2,3] * [3,2,1]~
%3 = 10

The same operator * is used for multiplying two scalars, multiplying a scalar by a matrix, and multiplying two matrices.

Vectors are 1×n matrices. * can be used for the dot product, but the transpose postfix operator ~ must be used on the 2nd matrix.

base conversion

number theory

combinatorics

ascii plots

mathics

mathematica compared

Mathics is an implementation of the Mathematica language. The underlying engine is SymPy.

Use pip to install it. Run the command line version with mathics:

$ pip install mathics

$ mathics

Or use mathicsserver to run a webserver which supports a notebook interface.

Solving equations:

In[1]:= Solve[x^2 + 2x + 1 == 0, x]
Out[1]= {{x -> -1}}

In[2]:= Solve[{2x+3y==7, 4x-y==7}, {x, y}]
Out[2]= {{x -> 2, y -> 1}}

Calculus:

In[1]:= D[x^3 + x + 3, x]
Out[1]= 1 + 3 x ^ 2

In[2]:= D[x^3 + x + 3, x] /. x -> 2
Out[2]= 13

In[3]:= D[Log[x], {x, 3}]
Out[3]= 2 / x ^ 3

In[4]:= Integrate[x^3 + x + 3, x]
Out[4]= 3 x + x ^ 2 / 2 + x ^ 4 / 4

In[5]:= Integrate[x^3 + x + 3, {x, 0, 1}]
Out[5]= 15 / 4
  • DSolve, RSolve
  • Simplify
  • Factor, Expand
  • Together, Apart

excel

spreadsheet

  • sort
  • filter
  • group
  • graph

r

Best for statistics and graphing.

R installs itself on the command line on Mac OS X at r and on Ubuntu at R. Note that zsh has a built-in called r for repeating the last command. Use command r to by-pass the built-in.

hp-11c

A description of the HP-11C.

Dedicated calculator hardware is obsolete. For that matter calculators which display one number at a time are obsolete.

That said, I like having an HP-11C style calculator app on my iPhone. Why waste cerebral cortex learning something else. I chose the most skeuomorphic HP-11C app that I could find. The best HP-11C apps run the original ROM on a hardware emulator.

I like reverse Polish notation calculators because there is no need for paren keys. One can do more calculations without storing values in registers.

One can install a more capable HP-15C app instead. However, the HP-11C was what I owned back in the day. The HP-15C can perform complex and matrix arithmetic, but since the screen cannot display an entire matrix or even an entire complex number, it is an exercise in frustration.

bc

An arbitrary precision algebraic notation Unix command line calculator.

shell

Shells can perform arithmetic. The syntax is cumbersome, but it can save a context switch:

$ echo $(( 347 * 232 ))
80504

The zsh shell can perform floating point arithmetic but bash cannot and must resort to forking bc:

$ echo $(echo '3.14 * 5' | bc)

The fish shell has a built-in command math which takes a string as an argument:

$ math '1.1 * 2.3'

It is a wrapper to bc, so one may need to use scale to get decimal digits:

$ math '13 / 5'
2

$ math 'scale=3; 13 / 5'
2.600

browser

One can perform arithmetic by searching on the arithmetic expression. The search engine will probably infer that you are trying to do a calculation and show the result. Google puts the result in the display of a working calculator implemented in JavaScript.

http://www.wolframalpha.com/ implements a portion of the Mathematica language. Try searching for

Solve[3x + 2 == 9x - 17, {x}]

Both of these techniques require opening a web page in a new tab. One can calculate without leaving the current page by dropping into the debugger:

mac windows
chrome ⌥⌘J Ctrl+Shift+J
firefox ⌥⌘K Ctrl+Shift+K
safari ⌥⌘C

Try this:

> Math.log(10)

In Safari, one must first enable the Develop menu in Preferences…

emacs

Using Emacs to perform a calculation is another way to avoid a context switch.

One can use M-: to enter and evaluate an Lisp S-expression in the minibuffer.

One can put the current buffer into M-x lisp-interaction-mode. The *scratch* buffer starts out in Lisp interaction mode. In Lisp interaction mode one can type Lisp S-expressions in the buffer and evaluate them. C-j writes the result in the buffer and C-x C-e echos the result in the minibuffer.

Another way to invoke Lisp from Emacs is M-x ielm. This creates a buffer with a Lisp REPL. Lisp expressions are evaluated as they are entered. It has command line history, but it is implemented in the slightly disconcerting (to me) Emacs way.

Emacs Common Lisp Emulation.

Emacs has a calc mode which sounds impressive on paper. It can perform matrix calculations, symbolic algebra manipulations, and graphing. I don't use it because it has a bit of a learning curve.

postgresql

Using the database can be regarded as a context switch saver:

> select 3.14 * 5;

Databases are good at statistics. count, sum, min, max, and avg are standard. PostgreSQL also has:

stddev_samp
stddev_pop
var_samp
var_pop
cor(X, Y)
cov_samp(X, Y)
cor_pop(X, Y)
regr_intercept(X, Y)
regr_slope(X, Y)

window functions

import and export

example of importing data and doing linear regression, scatterplot

Finding out what functions are available.

> select count(*) from pg_proc

> select count(*) from INFORMATION_SCHEMA.routines

glpsol

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