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Adjusting flow map styles in QGIS

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1

In a project, I am trying to adopt marvellous styles for a flow map created by Anita Graser a.k.a. @underdark.

---

At this moment I have the following outputs.

The sample of data can be found here. Styles in QML-format can be upload from this link.

Shapefile was created with the usage of Flow maps (Oursins) plugin).

Lines have different directions, i.e. the starting point of first is the ending point of the second and vice versa. So basically the table includes lines with both directions but without any description of directions.

---

However, I faced several problems

1. Proper allocation of arrows.

I am using an expression for Arrow type > Plain

CASE WHEN x(start_point($geometry)) - x(end_point($geometry)) < 0 THEN 1 ELSE 2 END

still, I can not properly allocate orange halves of Arrows on the opposite side of blues.

2. The width of the arrows.

I want to adjust the line width accordingly to the values of a field "FLUX".
For that reason, I am using an expression for Arrow width.

scale_linear( "FLUX" ,0,10,0.1,3) * CASE WHEN "FLUX" > 1000 THEN 1 ELSE 0 END

3. Varying buffers size.

Buffers around points shall inherit values from a different layer, i.e. they are not the same size.

Do I need to apply layer_property() function if I want to extract the value from a different layer or there is a much more efficient way of doing that? Right now the buffers around points defined with the following expression

`difference(

  difference(

    $geometry,

    buffer( start_point($geometry), 500 )

  ),

  buffer( end_point( $geometry), 500 )

)`

How to adjust 500 to other values that come from a different layer?

How shall I handle those issues?

---

My desired output should look like this, curved lines can be ignored.

---

References:

• QGIS-resource-collections


• Details of good flow maps


• New style: flow map arrows


• Representing network flows?


• Selecting features with same geometry in one shapefile

cartography qgis-2 flow-map

share|improve this question

edited 1 min ago

Taras

asked 2 days ago

TarasTaras

2,1172725

This question has an open bounty worth +50
reputation from Taras ending in 6 days.

This question has not received enough attention.

I would like to understand the way of adjusting styles for some layers programmatically.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thinking loud: Could you half the width of your arrows and then place them on one or the other side of your line? Like CASE WHEN x(start_point($geometry)) - x(end_point($geometry)) < 0 THEN -0.5 ELSE 0.5 END entered as "offset"-value (or use 1 instead of 0.5). Or is that not desirable for your intended style?
  
  – Erik
  2 days ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Unfortunately, not that much, I have to have a good looking map for further investigations and research. Your idea makes sense, but not what I dream about.
  
  – Taras
  2 days ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What's wrong with the direction and width of the arrows? It would help if you added an image of what you want the arrows to look like.
  
  – csk
  2 days ago
  

  
  
  
  

add a comment | 

1

In a project, I am trying to adopt marvellous styles for a flow map created by Anita Graser a.k.a. @underdark.

---

At this moment I have the following outputs.

The sample of data can be found here. Styles in QML-format can be upload from this link.

Shapefile was created with the usage of Flow maps (Oursins) plugin).

Lines have different directions, i.e. the starting point of first is the ending point of the second and vice versa. So basically the table includes lines with both directions but without any description of directions.

---

However, I faced several problems

1. Proper allocation of arrows.

I am using an expression for Arrow type > Plain

CASE WHEN x(start_point($geometry)) - x(end_point($geometry)) < 0 THEN 1 ELSE 2 END

still, I can not properly allocate orange halves of Arrows on the opposite side of blues.

2. The width of the arrows.

I want to adjust the line width accordingly to the values of a field "FLUX".
For that reason, I am using an expression for Arrow width.

scale_linear( "FLUX" ,0,10,0.1,3) * CASE WHEN "FLUX" > 1000 THEN 1 ELSE 0 END

3. Varying buffers size.

Buffers around points shall inherit values from a different layer, i.e. they are not the same size.

Do I need to apply layer_property() function if I want to extract the value from a different layer or there is a much more efficient way of doing that? Right now the buffers around points defined with the following expression

`difference(

  difference(

    $geometry,

    buffer( start_point($geometry), 500 )

  ),

  buffer( end_point( $geometry), 500 )

)`

How to adjust 500 to other values that come from a different layer?

How shall I handle those issues?

---

My desired output should look like this, curved lines can be ignored.

---

References:

• QGIS-resource-collections


• Details of good flow maps


• New style: flow map arrows


• Representing network flows?


• Selecting features with same geometry in one shapefile

cartography qgis-2 flow-map

share|improve this question

edited 1 min ago

Taras

asked 2 days ago

TarasTaras

2,1172725

This question has an open bounty worth +50
reputation from Taras ending in 6 days.

This question has not received enough attention.

I would like to understand the way of adjusting styles for some layers programmatically.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thinking loud: Could you half the width of your arrows and then place them on one or the other side of your line? Like CASE WHEN x(start_point($geometry)) - x(end_point($geometry)) < 0 THEN -0.5 ELSE 0.5 END entered as "offset"-value (or use 1 instead of 0.5). Or is that not desirable for your intended style?
  
  – Erik
  2 days ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Unfortunately, not that much, I have to have a good looking map for further investigations and research. Your idea makes sense, but not what I dream about.
  
  – Taras
  2 days ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What's wrong with the direction and width of the arrows? It would help if you added an image of what you want the arrows to look like.
  
  – csk
  2 days ago
  

  
  
  
  

add a comment | 

In a project, I am trying to adopt marvellous styles for a flow map created by Anita Graser a.k.a. @underdark.

---

At this moment I have the following outputs.

The sample of data can be found here. Styles in QML-format can be upload from this link.

Shapefile was created with the usage of Flow maps (Oursins) plugin).

Lines have different directions, i.e. the starting point of first is the ending point of the second and vice versa. So basically the table includes lines with both directions but without any description of directions.

---

However, I faced several problems

1. Proper allocation of arrows.

I am using an expression for Arrow type > Plain

CASE WHEN x(start_point($geometry)) - x(end_point($geometry)) < 0 THEN 1 ELSE 2 END

still, I can not properly allocate orange halves of Arrows on the opposite side of blues.

2. The width of the arrows.

I want to adjust the line width accordingly to the values of a field "FLUX".
For that reason, I am using an expression for Arrow width.

scale_linear( "FLUX" ,0,10,0.1,3) * CASE WHEN "FLUX" > 1000 THEN 1 ELSE 0 END

3. Varying buffers size.

Buffers around points shall inherit values from a different layer, i.e. they are not the same size.

Do I need to apply layer_property() function if I want to extract the value from a different layer or there is a much more efficient way of doing that? Right now the buffers around points defined with the following expression

`difference(

  difference(

    $geometry,

    buffer( start_point($geometry), 500 )

  ),

  buffer( end_point( $geometry), 500 )

)`

How to adjust 500 to other values that come from a different layer?

How shall I handle those issues?

---

My desired output should look like this, curved lines can be ignored.

---

References:

• QGIS-resource-collections


• Details of good flow maps


• New style: flow map arrows


• Representing network flows?


• Selecting features with same geometry in one shapefile

cartography qgis-2 flow-map

share|improve this question

edited 1 min ago

Taras

asked 2 days ago

TarasTaras

2,1172725

`difference(

  difference(

    $geometry,

    buffer( start_point($geometry), 500 )

  ),

  buffer( end_point( $geometry), 500 )

)`

share|improve this question

edited 1 min ago

Taras

asked 2 days ago

TarasTaras

2,1172725

share|improve this question

edited 1 min ago

Taras

asked 2 days ago

TarasTaras

2,1172725

asked 2 days ago

TarasTaras

2,1172725

asked 2 days ago

TarasTaras

2,1172725