How can I have the line plot, with the data coming one by one? I have the code
import matplotlib.pyplot as plt
plt.ion()
plt.plot(1, 2)
plt.pause(2.5)
plt.plot(2, 5)
plt.pause(2.5)
but it does not show the line, if I add 'o' option in plot function or change the plot function to scatter function, it works fine, But I want a line with no markers, how can I do this?
To respond to the comment about "deleting the current plot", and to improve upon Stefano's answer a bit, we can use Matplotlib's object-oriented interface to do this:
import matplotlib.pyplot as plt
x = [0, 1, 2, 3, 4, 5, 6]
y = [3, 1, 4, 1, 5, 9, 2]
fig, ax = plt.subplots()
ax.set(xlim=(min(x), max(x)), ylim=(min(y), max(y)))
plt.ion()
(line,) = ax.plot([], []) # initially an empty line
timestep = 0.5 # in seconds
for i in range(1, len(x) + 1):
line.set_data(x[:i], y[:i])
plt.pause(timestep)
plt.show(block=True)
This version uses a single Line2D object and modifies its underlying data via set_data. Since Matplotlib doesn't have to draw multiple objects, just the one line, it should scale better once your data becomes large.
ax.set() at start, I won't have the data at start, it comes one by one, so can it change the limit of x and y axis dynamically, instead of call ax.set() each time a data comes? (if I use scatter() it just expend the limit automatically if needed, can this be like that?)
I tried the following code, according with my tests it works only if the plot is generated in an external window:
import matplotlib.pyplot as plt
plt.ion()
fig = plt.figure()
ax = fig.add_subplot(111)
ax.grid(True)
x = [4, 1, 5, 3, 8]
y = [1, 2, 9, 0, 2]
ax.set_xlim(0, 9)
ax.set_ylim(-1, 10)
for j in range(1, len(x)):
X = [x[j-1], x[j]]
Y = [y[j-1], y[j]]
ax = plt.plot(X, Y, mew = 5, ms = 5)
# mew and ms used to change crosses size
plt.pause(1)# one second of delay
plt.show()
If you are working on Spyder, in order to make the intepreter generating an external window whenever you call a plot you have to type
%matplotlib qt
on the intepreter (and not into the script file!) BEFORE running the previous lines of code
plotcalls, two "lines" with a single point each, so if you don't have any markers, it's invisible to the eye. Add your data to lists for x and y instead and plot those.