Clearing a matlibplot from a Tkinter GUI - json

Question

The image shows the GUI:
I am making a GUI with Tkinter which can show graphs which have been plotted with matplotlib.
The graphs get their x and y values from a JSON file.
The data from the JSON file gets collected by some code which I wrote (this code is included in the code below)
What works: The collecting of data from the JSON-file, plotting the data in a graph via matplotlib, and showing this graph on a tkinter canvas all works fine.
Problem: I cannot clear the canvas, such that I can display another graph based on data from another JSON file. I have to close the program, start it again, and select a different JSON file, if I want to see another graph.
Here is the code:
################################### GUI program for graphs #######################################
##### Scrollbar for the listbox #####
Myframe = Frame(inspect_data)
Myframe.pack(side=tk.LEFT, fill=Y)
my_scrollbar = Scrollbar(Myframe, orient=VERTICAL)
#####Listbox#####
vores_listebox = Listbox(Myframe, width=22, height=40,
yscrollcommand=my_scrollbar.set)
vores_listebox.pack(side=LEFT, expand=True)
my_scrollbar.config(command=vores_listebox.yview)
my_scrollbar.pack(side=LEFT, fill=Y)
Myframe.pack()
###### Button functions ######
path_us = ""
def vis_NS():
vores_listebox.delete(0, END)
# Husk at ændre mapper##
global path_us
path_us = "C://Users//canal//OneDrive//Dokumenter//AAU//3. semester//1//"
for x in os.listdir(path_us):
if x.endswith(".json"):
vores_listebox.insert(END, x)
def vis_OS():
global path_us
path_us = "C://Users//canal//OneDrive//Dokumenter//AAU//3. semester//2//"
vores_listebox.delete(0, END)
# De NS;OS,US,MS skal ligge i hver sin mappe#
for x in os.listdir(path_us):
if x.endswith(".json"):
vores_listebox.insert(END, x)
def vis_US():
vores_listebox.delete(0, END)
for x in os.listdir("C://Users//canal//OneDrive//Dokumenter//AAU//3. semester//2"):
if x.endswith(".json"):
vores_listebox.insert(END, x)
def vis_MS():
vores_listebox.delete(0, END)
for x in os.listdir("C://Users//canal//OneDrive//Dokumenter//AAU//3. semester//2"):
if x.endswith(".json"):
vores_listebox.insert(END, x)
#### Buttons #####
button1 = Button(inspect_data,
text="Normal screwing",
width=17,
height=2,
bg="white",
fg="black",
command=vis_NS
)
button1.place(x=5, y=10)
button2 = Button(inspect_data,
text="Over screwing",
width=17,
height=2,
bg="white",
fg="black",
command=vis_OS
)
button2.place(x=5, y=50)
button3 = Button(inspect_data,
text="Under screwing",
width=17,
height=2,
bg="white",
fg="black",
command=vis_US
)
button3.place(x=5, y=90)
button4 = Button(inspect_data,
text="Missing screw",
width=17,
height=2,
bg="white",
fg="black",
command=vis_MS
)
button4.place(x=5, y=130)
######en fil bliver trykket#####
# placing the canvas on the Tkinter window
def items_selected(event):
selected_indices = vores_listebox.curselection()
selected_json = ",".join([vores_listebox.get(i) for i in selected_indices])
full_file_path = path_us + selected_json
open_json = js.load(open(full_file_path, "r"))
time = [open_json['XML_Data']
['Wsk3Vectors']['X_Axis']['Values']['float']]
rpm = [open_json['XML_Data']['Wsk3Vectors']
['Y_AxesList']['AxisData'][0]['Values']['float']]
torque = [open_json['XML_Data']['Wsk3Vectors']
['Y_AxesList']['AxisData'][1]['Values']['float']]
current = [open_json['XML_Data']['Wsk3Vectors']
['Y_AxesList']['AxisData'][2]['Values']['float']]
angle = [open_json['XML_Data']['Wsk3Vectors']
['Y_AxesList']['AxisData'][3]['Values']['float']]
depth = [open_json['XML_Data']['Wsk3Vectors']
['Y_AxesList']['AxisData'][4]['Values']['float']]
####### Using Matlib.pyplot to plot 5 graphs #######
plt.rcParams["figure.figsize"] = (7, 10)
plt.subplot(5, 1, 1)
plt.scatter(time, rpm, c="b", linewidths=2,
marker=",", edgecolor="b", s=1, alpha=0.5)
plt.title(selected_json)
plt.gca().axes.xaxis.set_ticklabels([])
plt.ylabel("RPM")
plt.grid()
plt.subplot(5, 1, 2)
plt.scatter(time, torque, c="g", linewidths=1,
marker=",", edgecolor="g", s=1, alpha=0.3)
plt.gca().axes.xaxis.set_ticklabels([])
plt.ylabel("Torque [Nm]")
plt.grid()
plt.subplot(5, 1, 3)
plt.scatter(time, current, c="r", linewidths=2,
marker=",", edgecolor="r", s=1, alpha=0.5)
plt.gca().axes.xaxis.set_ticklabels([])
plt.ylabel("Current [Amps]")
plt.grid()
plt.subplot(5, 1, 4)
plt.scatter(time, angle, c="m", linewidths=2,
marker=",", edgecolor="m", s=1, alpha=0.5)
plt.gca().axes.xaxis.set_ticklabels([])
plt.ylabel("Angle [RAD]")
plt.grid()
plt.subplot(5, 1, 5)
plt.scatter(time, depth, c="c", linewidths=2,
marker=",", edgecolor="c", s=1, alpha=0.5)
plt.xlabel("Time [ms]")
plt.ylabel("Depth [mm]")
plt.grid()
#### Sowing all the subplots in a tkinter canvas ########
fig = plt.figure()
canvas = FigureCanvasTkAgg(fig, master=inspect_data)
canvas.get_tk_widget().pack(side=tk.LEFT, fill=tk.BOTH, expand=True)
# toolbar = matplotlib.NavigationToolbar2TkAgg(
# canvas, self)
# toolbar.update()
canvas.get_tk_widget().pack(side=tk.TOP, fill=tk.BOTH, expand=True)
vores_listebox.bind('<<ListboxSelect>>', items_selected)
root.after(1000, converter)
root.mainloop()
I have tried canvas.delete(all), plt.clf() among other things. One solution I think could work is:
If I start the function def items_selected to clear the figure inside the canvas by using: plt.clf(fig), however "fig" is not defined at this point, so python wouldn't know what this means.

Answer 1

it seems to me that the problem originates from plotting to plt, and not directly onto some axis from a figure linked to tkinter. Try to bind your subplot figure directly to your canvas outside the items_selected() function, and then redraw the canvas whenever you change the underlying matplotlib figure:
fig, axes = plt.subplots(5, 1, figsize=(7, 10))
canvas = FigureCanvasTkAgg(fig, inspect_data)
canvas.get_tk_widget().pack(side=tk.LEFT, fill=tk.BOTH, expand=True)
def items_selected(event):
.....
axes[0].scatter(time, rpm, c="b", linewidths=2,
marker=",", edgecolor="b", s=1, alpha=0.5)
axes[0].set_title(selected_json)
axes[0].set_xticklabels([])
axes[0].set_ylabel("RPM")
axes[0].grid()
....
canvas.draw()