add a basic heatmap example

plot/examples/basic_heatmap.v

@@ -0,0 +1,23 @@
+module main
+import vsl.plot
+
+
+z := [[1.0, 0, 30, 50, 1], [20.0, 1, 60, 80, 30], [30.0, 60, 1, -10, 20]]
+x := ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
+y := ['Morning', 'Afternoon', 'Evening']
+
+mut plt := plot.new_plot()
+
+plt.add_trace(
+	trace_type: .heatmap
+	x_str: x
+	y_str: y
+	z: z
+)
+plt.set_layout(
+	title: 'Heatmap Basic Implementation'
+	width: 750
+	height: 750
+)
+
+plt.show()?

plot/trace.v

@@ -15,6 +15,7 @@ pub mut:
 	trace_type    TraceType      [required]
 	x             []f64
 	x_str         []string
+	y_str		  []string
 	xbins         map[string]f32
 	y             []f64
 	z             [][]f64

remove.py

@@ -0,0 +1,49 @@
+import plotly.graph_objects as go
+import numpy as np
+
+# Build the rectangles as a heatmap
+# specify the edges of the heatmap squares
+phi = (1 + np.sqrt(5) )/2. # golden ratio
+xe = [0, 1, 1+(1/(phi**4)), 1+(1/(phi**3)), phi]
+ye = [0, 1/(phi**3), 1/phi**3+1/phi**4, 1/(phi**2), 1]
+
+z = [ [13,3,3,5],
+      [13,2,1,5],
+      [13,10,11,12],
+      [13,8,8,8]
+    ]
+
+fig = go.Figure(data=go.Heatmap(
+          x = np.sort(xe),
+          y = np.sort(ye),
+          z = z,
+          type = 'heatmap',
+          colorscale = 'Viridis'))
+
+# Add spiral line plot
+
+def spiral(th):
+    a = 1.120529
+    b = 0.306349
+    r = a*np.exp(-b*th)
+    return (r*np.cos(th), r*np.sin(th))
+
+theta = np.linspace(-np.pi/13,4*np.pi,1000); # angle
+(x,y) = spiral(theta)
+
+fig.add_trace(go.Scatter(x= -x+x[0], y= y-y[0],
+     line =dict(color='white',width=3)))
+
+axis_template = dict(range = [0,1.6], autorange = False,
+             showgrid = False, zeroline = False,
+             linecolor = 'black', showticklabels = False,
+             ticks = '' )
+
+fig.update_layout(margin = dict(t=200,r=200,b=200,l=200),
+    xaxis = axis_template,
+    yaxis = axis_template,
+    showlegend = False,
+    width = 700, height = 700,
+    autosize = False )
+
+fig.show()