Hi all,

Iâ€™m creating a heatmap with a discrete colormap following this guide.

I noticed that when my `z`

variable is one dimensional, the colorbar displays ticks in incorrect locations.

Here is the guideâ€™s original code:

```
def discrete_colorscale(bvals, colors):
"""
bvals - list of values bounding intervals/ranges of interest
colors - list of rgb or hex colorcodes for values in [bvals[k], bvals[k+1]],0<=k < len(bvals)-1
returns the plotly discrete colorscale
"""
if len(bvals) != len(colors) + 1:
raise ValueError('len(boundary values) should be equal to len(colors)+1')
bvals = sorted(bvals)
nvals = [(v - bvals[0]) / (bvals[-1] - bvals[0]) for v in bvals] # normalized values
dcolorscale = [] # discrete colorscale
for k in range(len(colors)):
dcolorscale.extend([(nvals[k], colors[k]), (nvals[k + 1], colors[k])])
return dcolorscale
bvals = [2, 15, 40, 65, 90]
colors = ['#09ffff', '#19d3f3', '#e763fa' , '#ab63fa']
dcolorsc = discrete_colorscale(bvals, colors)
bvals = np.array(bvals)
tickvals = [np.mean(bvals[k:k + 2]) for k in range(len(bvals) - 1)] # position with respect to bvals where ticktext is displayed
ticktext = [f'<{bvals[1]}'] + [f'{bvals[k]}-{bvals[k+1]}' for k in range(1, len(bvals)-2)]+[f'>{bvals[-2]}']
z = np.random.randint(bvals[0], bvals[-1]+1, size=(20, 20))
heatmap = go.Heatmap(z=z,
colorscale=dcolorsc,
colorbar=dict(
thickness=25,
tickvals=tickvals,
ticktext=ticktext,
))
fig = go.Figure(data=[heatmap])
fig.update_layout(width=500, height=500)
fig.show()
```

Now do the same thing, but only display the first line of `z`

:

```
heatmap = go.Heatmap(z=[z[0]],
colorscale=dcolorsc,
colorbar=dict(
thickness=25,
tickvals=tickvals,
ticktext=ticktext,
))
fig = go.Figure(data=[heatmap])
fig.update_layout(width=500, height=500)
fig.show()
```

Thereâ€™s a slight but significant change in the location of colorbar ticks: