support "lineStyle" arguments

[bukkideme]

You already implemented selectable marker shapes for Plots, which is great! What do you think, could it be possible to also implement dashed line types (like dotted, dash, dash/dots, etc)?
In this case, I think the legend section could automatically show marker shapes / line types, depending on the following conditions:

1. We have larger than zero for both marker shapes and line widths: show both markers and (dashed) lines in legend section.
2. If either the line width or the marker shape zero valued, reflect this info in legend: for example in case of zero sized marker, only show line. In the recent Legend behavior, the marker shows up even if we only plot the line and set marker size to zero.

I will really try to find some time later on to do some real contribution to the code base, sorry that recently I can only provide such limited help...

[swharden]

It would be great to be able to plot dotted, dashed, and other patterns of lines. I think the only plottable objects which would benefit from this are scatter plots and axis lines.

This should be easy to implement too. Lines are drawn with Pen objects. These objects are created here for scatter plots and here for axis lines. Pen objects are currently all set to draw solid lines, but they can be easily customized to draw different patterns by setting their DashStyle:

pen.DashStyle = DashStyle.DashDot;

Once implemented, the legend code could be updated to draw proper dash styles too.

The website
http://csharphelper.com/blog/2015/02/draw-dashed-lines-with-different-styles-in-c/ displays some common styles:

[Padanian]

I’ll give it a try. Would you please in the meantime inspect the possibility to make Plottable class serializable? I’m having a hard time at time at that.

[Padanian]

Looks difficult to combine the mark symbol with the line type, though. Do we need to put the line type aside the mark symbol and enlarge the legend frame?

[swharden]

The legend could just show line (with its DashStyle) and place a single marker above it (if markers are being used).

# python example
import matplotlib.pyplot as plt
import numpy as np
xs = np.arange(20)
ys = np.sin(np.pi*2*xs/len(xs))
plt.plot(xs, ys, label='data', linestyle=':',
    marker='v', markerfacecolor='r', markeredgewidth=0)
plt.legend()
plt.show()

[Padanian]

Ok, but I think we have to face a minor drawback. The dash spacing is exactly as wide as line thickness, therefore it looks like this. I think we need to redefine the styles. What do you think.

[swharden]

@Padanian did you try to post a picture with your last message? I'm viewing the GitHub issue page #59 and no image appeared with your last post.

[Padanian]

Yes, this one

Do I need to redefine dashes and spaces?

[swharden]

It looks like a pretty good start! Let's add some custom dash patterns into the mix so we can always add/modify patterns later. I think you make custom patterns like:

Pen pen = new Pen(Color.Black, 5);
float[] dashValues = { 5, 2, 15, 4 };
pen.DashPattern = dashValues;

[swharden]

... actually, maybe all our patterns should be custom? Maybe the dash values are some multiple of line width?

[Padanian]

Yes, all of them need to be custom, to properly render. I’m working on it. Will commit later tonight.

[Padanian]

[swharden]

Yes, all of them need to be custom, to properly render. I’m working on it. Will commit later tonight.

Sounds great! Thanks for your contribution! It's looking great already.

[bukkideme]

Another thing I noticed about Legends, sometimes it could be useful to change their size / font type. As for example, we have in the case of the PlotText() method.
The "fontName", "fontSize", "bold" inputs could be also very useful for the Legend() method. What do you think, when we increase/decrease font size in a legend, should the legend markers follow these size changes too? I guess it would look nicer...

[swharden]

A review of fonts for the title, axis labels, legend, and PlotText() is a good idea! Some of these features are implemented and some aren't, but a review of each of these methods to fill-in the missing features and ensure consistency would be an improvement for sure. I started an issue devoted to this topic #61

Regarding the marker size in the legend, I think it should reflect the marker size in the plot itself. Scatter plots could code plot groups by marker size, so since that may be its own metric let's stick to drawing it "actual size" in the legend.

[swharden]

Regarding the marker size in the legend, I think it should reflect the marker size in the plot itself. Scatter plots could code plot groups by marker size, so since that may be its own metric let's stick to drawing it "actual size" in the legend.

This also makes me think we should probably should draw the lines in the legend as their actual size, since lineWidth might be used to separate groups of data... @Padanian do you want to make this change?

[Padanian]

It can end up in a disproportioned marker in the legend.

[Padanian]

It'll be awful. Been there, done that. That's why I set it to fixed linewidth.

[bukkideme]

It'll be awful. Been there, done that. That's why I set it to fixed linewidth.

I also think that line width in Legend does not need to match the plotted line width. Same applies to symbol/marker size. However, if we increase the font size (option will be in a later release) in the Legend, the marker/line symbols might become unproportionally small compared to it. Should the marker/line symbol size be scaled with the Legend font size? What do you think?

Actually the visibility of the Legend marker next to the text in the recent version also feels a little bit small, difficult to see the colored dots front of the Legend text lines...

[Padanian]

  I agree the marker symbol should be proportioned to the font size, but not to the marker size.When font size selection would be available, a small correction to the legend code might be necessary.If you like the marker symbol to be bigger as it is, we could scale it up a little bit.

[Padanian]

Marker size to reflect legend font size is ready to request pull, but you already got a pull request ahead. Please pull it before this or delete it.

[swharden]

Just pulled @Padanian's branch into the master (#60). I called the argument "lineStyle" to be consistent with matplotlib's naming convention. I also added an example to the cookbook:

https://github.com/swharden/ScottPlot/tree/master/cookbook#custom-linestyles

Thanks @Padanian!

[marc-frank]

Hi, I used this:
formsPlot1.Plot.AddCircle(x: midpoint.X, y: midpoint.Y, radius: radius, color: Color.Gray, lineWidth: 1, lineStyle: ScottPlot.LineStyle.Dash);
But the line draws solid.