Although it isn't a GIS Tool, this is something you could use Gephi for. Especially if you want it to look like your illustration. Straight lines, no problem. Curves are more challenging.
Gephi is for network analysis and plotting. It's typically used for things like social network analysis (e.g. analysing Facebook or Twitter networks)
This example shows a ...
In December 2012, Esri has published a tool for generating flow maps. It is written in Python and available for ArcGIS Desktop users. And there is a ArcGIS Blogs post on generating flow maps with the links to the tool, some more information, and test data for the tool. I believe this is the kind of tool you would use to generate trade flows, too.
You are changing the line width of the wrong component (the 'fill' texture of the arrow).
You need to go to the Arrow section (Flèche) and change the arrow width, etc. there.
Have a close look at this screenshot from Anita's tutorial and see where she has used expressions/columns to modify arrow width on the right-hand side.
See also her post here on ...
SAGA's flow directions are coded from North = 0 :
7 0 1
5 4 3
Each GIS has its codification : for GRASS it's
3 2 1
5 6 7
and for ARcgis : http://desktop.arcgis.com/fr/arcmap/10.3/tools/spatial-analyst-toolbox/how-flow-direction-works.htm
For a pure QGIS solution, check https://anitagraser.com/2019/05/04/flow-maps-in-qgis-no-plugins-needed/
The key is to create a virtual layer: Virtual Layers: Layer | Add Layer | Add/Edit Virtual Layer
SELECT StartID, DestID, Weight,
JOIN nodes a ON edges.StartID = a.ID
JOIN nodes b ON edges.DestID = b.ID
There is a distributive flow tool available in the applications prototype lab.
Here is a blog and some links and data.
Even if you are not looking for this.
I like it so here.
Credit: Brad Simantel
With your edit addition to the question I will add this link for placing line decorations with code.
If you desire more help on using arrows add to your ...
Here is an illustration of the workflow I mentioned in the comment above, and although I don't know of any simple pre-canned routine to do this, I have attached an excel spreadsheet that one can import a set of origin-destination coordinates and the sheet then makes a set or circular line coordinates (spreadsheet here). It has formulas set up so it is pretty ...
I've always been fond of a colour ramp that I use for visualizing flow accumulation (not that unlike your application) that transitions from black to blue to yellow to pale yellow. It does an excellent job of highlighting the high-value areas, gives good contrast within areas of low values and seems to be a bit warmer and less 'ghostly' than the blue-to-...
Hopefully you are using QGIS 3.0, as it has new offset_curve() function.
In the above example "offset" is the field name you have mentioned.
[EDIT] In response to the update by @auslander.
Revised geometry generator syntax: (should work for QGIS 2.18 & QGIS 3.0)
This is a still-unresolved issue in QGIS. There are lots of symbology options, and some of them will not be reflected in the legend. If you visit the issue tracker page, you will find multiple open bug reports and feature requests about this type of issue.
Here are a couple of workarounds:
If the arrow width appears correctly anywhere in the program (eg ...
Look at the recent PLOS paper by Hristova et al. (2016) 'The International Postal Network and Other Global Flows as Proxies for National Wellbeing'. They list several, global openly available datasets:
World Trade Network available from the MIT Atlas Project (https://atlas.media.mit.edu/about/data/sources/)
GlobalMigration Network available from the Global ...
Please check that your data is in correct format. Decimal separator is "." point and items are tab or space delimited.
At first, it might be better to run the plugin with the test data provided under the installation folder. (or download the plugin from http://cempro.dyndns.org/FlowMapper-0.4.zip and extact the sample data)
Interaction matrix should be ...
Clearly a bit delayed, but this question: How to make radial flow map showing curved lines over short distances links to a great article by Esri called Creating radial flow maps with ArcGIS that will help answer your question.
Using the techniques described in the article, you can use the XY to Line tool in order to create your curved map. I put together a ...
After a long and painful process, I found a way to do it combining GRASS GIS and QGIS with GRASS.
Here is how I did it:
In QGIS load the DEM raster.
Using GRASS for QGIS run the r.watershed command (from the processing toolbox) setting an appropriate threshold.
In my case, I always try to make the watershed no bigger than the “acceptable area limit” for ...
I am the developer of qgis flowmapper plugin. I would be please to answer any questions regarding the plugin.
A readme and tutorial data is already included within the zip file that you have downloaded either from the plugin repo or from the website www.cempro.tk
Briefly, supply (i) input node coordinates as text file and (ii) flow data matrix as text file ...
I haven't used it myself so far, but i think that the Flow Mapper Plugin would be the way to go.
If you can't find the plugin, try checking "show all plugins, even those marked as experimental" under the Plugins -> Fetch python plugins -> Tab:Options
To get additional info on the plugin, browse to your .qgis folder within your users folder.
There are a variety of different flow mapping software that work on Macs. Below are some links to pages where you can find more information about downloading these software:
Phan et. al Flow Map Layout: http://graphics.stanford.edu/papers/flow_map_layout/
QGIS FlowMapper plugin: install plugin in QGIS
The QGIS flow ...
A search with Google threw up these pages...
Someone has even created a tool that flows around country boundaries.
Take a look at Color Brewer, a site that helps you to pick color schemes that are well-suited for communicating particular types of data.
(I copied this description from this Wired article about Cindy Brewer, the creator of the site).
Without more information about your data it's only guesswork why the process isn't working for you. A way around this could be to use the Points to line function instead.
In this case you only have one column with all of your points, end points and start points, together. The key here is to connect them with a new field, where the two points that should be ...
I have recently faced the same problem and handled it.
Therefore, I am providing some hints for those who are still struggling.
Text file (.txt) that stores node coordinates should be in the following format:
No columns titles, e.g. long, lat.
Coordinates go only with dots
Space in between long and lat, not TAB.
Text file (.txt) that defines flow matrix ...
1. Varying buffers size
I would recommend you to join the attributes of both layers instead of fetching layer properties. These are the expressions I used in this example:
Point layer size:
scale_exp("attributeBuffer", minTotalFlux, maxTotalFlux, @min, @max, exponent)
Geometry generator of line layer:
I had to do something similar once and I used RT QSpider plugin.
Install the plugin RT QSpider in Plugins > Manage and Install plugins
Add the coordinates inside the attribute table of your shapefile of locations (if it is not already the case). To do so, you can use the tool in Vector > Geometry Tools > Export/Add geometry columns. It will create ...
You could add a new text field called 'direction' and then use calculate field with a case statement to work out if the line goes north or south. eg.
CASE WHERE coord_y2 > coord_y1
You can then use a rule based style to offset the northerly and/or southerly lines
You cannot save arrows in a shapefile. Drawing arrows depends on the software you want to import the exported shapefile. For example in ArcGIS you can simply define a symbology for the line feature to have an arrow along the direction that the linear feature is sketched.
Just try to avoid green to red color ramps considering the color-blind population that may have difficulty interpreting your results. I am green/red color-blind and get frustrated when cartographers/GIS mapmakers use this option.
The Spider graph tool might be able to help you here, but it would require a degree of manipulation to get right - which if you're proficient in photoshop you might be better off doing it in there, pending the complexity of the data.
As a really rough guide, and shamelessly lifted from Pete over at MI-L:
Keep your base data file, but create a 2nd file for ...