Add vertical and horizontal lines

Author: ruivieira

docs/README.md

@@ -96,4 +96,26 @@ figure5.add lp5
 figure5.add newTitle("A plot with a title (in Courier New).")
 ```
 
-![plot](plot_title.png)
+![plot](plot_title.png)
+
+### vertical and horizontal lines
+
+```nim
+let figure6 = newFigure()
+let x6 = toSeq(0..1000)
+let y6 = x5.map(func(k:int):float = sin(float(k) / 50.0))
+let lp6 = newLinePlot(x5, y5)
+lp6.colour = "red"
+figure6.add lp6
+let hl6 = newHorizontalLine(0)
+hl6.linestyle = "--"
+hl6.colour = "black"
+figure6.add hl6
+for i in 0..6:
+    let vl6 = newVerticalLine(PI * float(i) * 50.0)
+    vl6.linestyle = "-."
+    vl6.colour = "blue"
+    figure6.add vl6
+```
+
+![plot](plot_hv_lines.png)

docs/plot_hv_lines.png

@@ -144,4 +144,44 @@ type Title = ref object of Plot
   title*: string
 method render(this: Title): string = fmt"plt.title(r'{this.title}')"
 
-proc newTitle*(title: string): Title = Title(title: title)
+proc newTitle*(title: string): Title = Title(title: title)
+
+# Horizontal line
+type HorizontalLine[A] = ref object of Plot
+  y*: A
+  linestyle*: string
+  colour*: string
+method render[A](this: HorizontalLine[A]): string =
+  var options: seq[string] = @[]
+  if this.linestyle!="":
+    options.add fmt"linestyle='{this.linestyle}'"
+  if this.colour!="":
+    options.add fmt"color='{this.colour}'"
+  if len(options)>0:
+    let optstr = options.join(",")
+    return fmt"plt.axhline(y={this.y}, {optstr})"
+  else:
+    return fmt"plt.axhline(y={this.y})"
+
+proc newHorizontalLine*[A](y: A): HorizontalLine[A] =
+  HorizontalLine[A](y: y, linestyle: "", colour: "")
+
+# Vertical line
+type VerticalLine[A] = ref object of Plot
+  x*: A
+  linestyle*: string
+  colour*: string
+method render[A](this: VerticalLine[A]): string =
+  var options: seq[string] = @[]
+  if this.linestyle!="":
+    options.add fmt"linestyle='{this.linestyle}'"
+  if this.colour!="":
+    options.add fmt"color='{this.colour}'"
+  if len(options)>0:
+    let optstr = options.join(",")
+    return fmt"plt.axvline(x={this.x}, {optstr})"
+  else:
+    return fmt"plt.axvline(x={this.x})"
+
+proc newVerticalLine*[A](x: A): VerticalLine[A] =
+  VerticalLine[A](x: x, linestyle: "", colour: "")