Creating a spectrum plot with callback #525

Hello all,
I have a csv file with 15 soil samples. each sample has some parameters like: OM and Clay and in addition it has a spectrum (starting from 400 until 750).
Im trying to create a dashboard with 3 sections:

1. Plot of Clay vs. Sand
2. stats data
3. spectrum graph from 400 until 750.

and i would like the stats data and the spectrum graph to be updated automatically when i hover over a certain point in the first plot.
I was able to do so with the stats data, however, I was not able to do it with the spectrum.
I dont know if i was reading the data correctly or I had a problem with the callback.

Im new to python and dash so I would need your assistance
Thank you

import dash
import dash_core_components as dcc
import dash_html_components as html
import plotly
import plotly.plotly as py
import plotly.graph_objs as go
import plotly.offline as pyo
import pandas as pd
import cufflinks as cf
from dash.dependencies import Input, Output

app = dash.Dash()

df = pd.read_csv('test_GitHub.csv', index_col=None, na_values=['NA'],sep=',',low_memory=False)

app.layout = html.Div([ #global title
html.Div([ #header
html.H1('Title'),
html.H3('Additional title')
]),
html.Div([
dcc.Graph(
id = 'test_scatter',
figure = {
'data': [go.Scatter(
x = df['Clay'],
y = df['Sand'],
text = df['Soil'],
hoverinfo = ['text','x','y'],
mode = 'markers'
)],
'layout': go.Layout(
title = 'Plot',
xaxis = {'title': 'Clay'},
yaxis = {'title': 'Sand'},
hovermode = 'closest'
)}),
dcc.Markdown(
id = 'stats',
),
dcc.Graph(
id = 'spec',
figure = {
'data': [go.Scatter(
x = df['400':'750'],
y = df.iloc[soil_index]['400':'750'],
text = df['Soil'],
hoverinfo = ['text','x','y'],
mode = 'markers'
)],
'layout': go.Layout(
title = 'Spectrum',
xaxis = {'title': 'Wavelength (nm)'},
yaxis = {'title': 'Value'},
hovermode = 'closest'
)})
],style = {'width': '50%', 'height': '50%', 'display': 'inline-block'})])

@app.callback(
Output('stats', 'children'),
[Input('test_scatter','hoverData')])

def callback_stats(hoverData):
soil_index = hoverData['points'][0]['pointIndex']
stats = """
The soil is located in Latitude {} and Longitude {} and contains:

    {}(%) Organic Matter
    {}(% wt.) Clay
    {}(% wt.) Silt
    {}(% wt.) Sand
    """.format(df.iloc[soil_index]['OM'],
                df.iloc[soil_index]['Clay'],
                df.iloc[soil_index]['Silt'],
                df.iloc[soil_index]['Sand'])
return stats

@app.callback(
Output('spec', 'children'),
[Input('test_scatter','hoverData')])

def callback_spec(hoverData):
soil_index = hoverData['points'][0]['pointIndex']

return stats

if name == 'main':
app.run_server()

test_GitHub.txt