`fastscatterm` documentation

The `fastscatterm` function places color-scaled point markers on map coordinates. This is a much faster version of the Mapping Toolbox's `scatterm` function, adapted from Aslak Grinsted's `fastscatter`.

## Contents

## Syntax

fastscatterm(lat,lon,C) fastscatterm(...,MarkerType) fastscatterm(...,'MarkerProperty',MarkerValue) h = fastscatterm(...)

## Description

`fastscatterm(lat,lon,C)` places markers at geocoordinates `lat`, `lon`, color-scaled to values in array `C`.

`fastscatterm(...,MarkerType)` specifies a `MarkerType` as `'+'`, `'x'`, `'o'`, etc. Default `MarkerType` is `'.'`.

`fastscatterm(...,'MarkerProperty',MarkerValue)` specifies any MarkerSpec preferences as propery name-value pairs. For example, `fastscatterm(lat,lon,z,'markersize',30)`.

`h = fastscatterm(...)` returns a handle `h` of plotted mesh object.

## Requirements

This function requires Matlab's Mapping Toolbox.

## Example 1: Comparing `scatterm` and `fastscatterm`

Here we compare Matlab's inbuilt `scatterm` with `fastscatterm`. First create 200,000 random data points:

N = 200000; lat = 20*randn(N,1); lon = 15 + 10*randn(N,1); z = 8+7*cosd(lat)+2*sind(lon)+randn(N,1);

Plot with Matlab's `scatterm` function and use `tic` `toc` to calculate plotting time:

figure worldmap('africa') tic scatterm(lat,lon,15,z,'filled') scattermtime = toc caxis([7 20])

scattermtime = 6.2777

Make an equivalent plot with `fastscatterm`:

```
figure
worldmap('africa')
tic
fastscatterm(lat,lon,z)
fastscattermtime = toc
caxis([7 20])
```

fastscattermtime = 0.1424

The difference in plotting time for `scatterm` versus `fastscatterm` is quite staggering. See:

scattermtime/fastscattermtime

ans = 44.0901

Matlab's inbuilt `scatterm` function requires more than 40 times more processing time than `fastscatterm` for 200,000 points.

## Example 2: Formatting:

Create 10 points of example data:

N = 10; lat = 20*randn(N,1); lon = 15 + 10*randn(N,1); z = 8+7*cosd(lat)+2*sind(lon)+randn(N,1);

Plot the example data as big fat plus signs:

figure worldmap('africa') fastscatterm(lat,lon,z,'+','markersize',30,'linewidth',15)

## Author Info

This function was mostly written by Aslak Grinsted in 2014 based on an idea by Boris Babic (http://www.mathworks.com/matlabcentral/newsreader/view_thread/22966). In October 2015, Chad A. Greene of the University of Texas at Austin's Institute for Geophysics merely added some coordinate transformation bits, some error checks, and a little bit of documentation.