Hi @Joaquim, thank you for your giving me some hints. I experimented quite a bit with it but I got stuck. Here is what I got so far:
I used a base grid in a pattern as seen in panel a) in 0.25 zoomed (first row). The columns are 0.5 units apart in x and y direction. Then I added some noise in x and y direction. Here I present two different increments:
Panel a) (except for the first row titled 0.25 zoomed) shows the built-in -Gp31 pattern as a reference.
Panel b) is the result of my experimentation with a symbol trying to mimic the built-in pattern
Panel c) is the comparison between the base grid (panel a) in first row) and the grid with the added noise.
The problems I observed:
Width the larges increment of +/-0.25 the points can get too close together and also further apart than I want it. See area around (5.5|6) for further apart; (5|0) and (9|4) for too close in 0.25 zoomed panels b) & c).
The smaller the increment, the larger the areas where there can’t be any point thus leading to a more geometric pattern which I want to avoid:
Not sure. But gmt spatial -Aa can be used to replace neighbors that are too close with their average. So that could help with your case at (9,4). If you could select parameters so that you dont get too many or any that are too far apart then perhaps this could work.
your way is way more elegant. Thank you for the tip with gmt spatial – it helped a lot with points too close together. But the empty areas remain (and occasionally got bigger) and I get some worm structures? I don’t really understand why some pairs and some triplets got deleted (panel c)) creating empty spaces.
Some further experimentation showed an interesting pattern. I’m not quite sure if it is supposed to clump like this in the middle when using gmt spatial -Aa. As far as I understand it – shouldn’t the blue points spread evenly across the plot?
Yes, I played with -Aa quite a bit, @pwessel. As long as the increment is < -I I get that funny behaviour. In the example case I used -Aa = -I / 2 = 0.5. Interestingly there are some new points (light blue) without obviously replaced points (red) nearby as well. One example is in panel c) about half way between the two lower left green circles (light blue dot).
Hi @joaquim, I basically want to create a configurable, infinite pattern -Gp31 which has no discernible pattern but at the same time has a uniform appearance. Configurable in this context means I can specify max and min distance between points. This is important to me as I want to place custom symbols at those points. The symbols are not allowed to overlap but also can’t be more than a specified max distance apart.
Yes, I understood that but was thinking in a real map example produced by someone else.
Perhaps another idea to try is to generate more x,y inside each cell and use block* to find the mean position. This number can not be high to avoid that the mean position falls over the cell center.
Sand (left side) and crescent-shaped dunes (right side) on current Phoenix Sectional Aeronautical Chart published by the Federal Aviation Administration – USA
Ai ai, that Gran Desierto is crazy. The sand grains however show some circular patterns. I made me think on Huygen’s principle for making waves after punctual sources.
@Joaquim you think of intersecting several wave patterns and using the crossing points as coordinates? The dunes aren’t that difficult – just custom symbols rotated to the local prevailing wind direction.
I’m just not sure if this really is the reason for this circular pattern you can see in the sand in the examples I provided. The sand has no definite center where the dots radiate out from.
I’m under the impression that the pattern might be from the artist dotting the area pattern by hand on the film master screen used for reproduction. So maybe it is more an example of the human limitation to make random patterns without introducing tidiness?
I think you are right about a human drawing of those patterns. On a second read the concentration near the center was on purpose to better reproduce what happens in a sunflower where new seeds at the center are smaller and of higher density.
