Set axis values in Matplotlib graph

Question

I am trying to plot two plots in one graph using matplotlib. Following is my code:

import matplotlib.pyplot as __plt


def plot(x, y, spec_x, spec_y):
    if None in (x, y, spec_x, spec_y) or '' in (x, y, spec_x, spec_y):
        raise ValueError
    else:
        __plt.xlim(min(spec_x), max(spec_x))
        __plt.ylim(min(spec_y), max(spec_y))
        __plt.plot(x, y, color='blue')
        __plt.plot(spec_x, spec_y, color='red', linestyle='dashed')
        __plt.xlabel('Frequencies (Hz)', fontsize=18)
        __plt.ylabel('Y Label', fontsize=16)
        __plt.xscale("log")
        __plt.yscale("log")
        __plt.grid(which='major', color='#DDDDDD', linewidth=0.8)
        __plt.grid(which='minor', color='#EEEEEE', linestyle=':', linewidth=0.5)
        __plt.savefig('test_graph.png', dpi=1000)
        __plt.clf()
        __plt.close()


if __name__ == "__main__":
    x1_l1 = [0.0, 1e-07, 1.20226443461741e-07, 1.31825673855641e-07, 1.44543977074593e-07, 1.58489319246111e-07,
             1.73780082874938e-07, 1.90546071796325e-07, 2.08929613085404e-07, 2.29086765276777e-07,
             2.51188643150958e-07, 2.75422870333817e-07, 3.01995172040202e-07, 3.31131121482591e-07,
             3.63078054770101e-07]

    y1_l1 = [-0.887961849042741, -0.887961849042741, -0.887961849042949, -0.887961849043086, -0.887961849043252,
             -0.887961849043453, -0.887961849043695, -0.887961849043987, -0.88796184904434, -0.887961849044765,
             -0.887961849045278, -0.887961849045896, -0.887961849046641, -0.887961849047538, -0.887961849048619]

    x1_l2 = [0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18,
             0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 10.0]

    y1_l2 = [0.638219, 0.321497, 0.216958, 0.165437, 0.135094, 0.115313, 0.101539, 0.0914968, 0.0839203, 0.078051,
             0.073407, 0.0696679, 0.066613, 0.0640855, 0.0619714, 0.0601859, 0.0586651, 0.0573596, 0.0562311, 0.0552495,
             0.0543905, 0.0536349, 0.052967, 0.0523738, 0.0518448, 0.0513711, 0.0509454, 0.0505615, 0.0502142, 0.049899, 1.908654]

    print(len(x1_l1))
    print(len(y1_l1))
    print(len(x1_l2))
    print(len(y1_l2))
    x1_l2_e = []
    x1_l1_e = []
    for e in x1_l2:
        x1_l2_e.append(format(e, 'f'))
    for f in x1_l1:
        x1_l1_e.append(format(f, 'f'))

    plot(x1_l1_e, y1_l1, x1_l2_e, y1_l2)

I want the graph and its axis both to be in the range of x1_l2_e and y1_l2. I am setting up axis min and max using xlim and ylim, but the code is giving me an incorrect graph. Below is how it looks like:

I was expecting more like the below graph:

Any help?

PS - The original data list has large number of elements. I am posting just a few here.

Mitchell van Zuylen · Accepted Answer · 2022-06-29 06:16:13Z

Okay, so there are a couple of problems with the code.

First, your call to xlim and ylim are currently ignored. You are currently calling these before you actually plot anything. As such, the axis are set and then overwritten when you actually plot something. As such, moving these calls below the calls to plot will already get you closer.

Next, you convert the following

x1_l1  = [0.0, 1e-07, 1.20226443461741e-07, 1.31825673855641e-07, 1.44543977074593e-07, 1.58489319246111e-07,
         1.73780082874938e-07, 1.90546071796325e-07, 2.08929613085404e-07, 2.29086765276777e-07,
         2.51188643150958e-07, 2.75422870333817e-07, 3.01995172040202e-07, 3.31131121482591e-07,
         3.63078054770101e-07]

x1_l1_e = []
for f in x1_l1:
    x1_l1_e.append(format(f, 'f'))

We can make this a little easier by doing the following with list comprehension:

x1_l1_e  = [0.0, 1e-07, 1.20226443461741e-07, 1.31825673855641e-07, 1.44543977074593e-07, 1.58489319246111e-07,
         1.73780082874938e-07, 1.90546071796325e-07, 2.08929613085404e-07, 2.29086765276777e-07,
         2.51188643150958e-07, 2.75422870333817e-07, 3.01995172040202e-07, 3.31131121482591e-07,
         3.63078054770101e-07]
x = [format(x, 'f') for x in x1_l1_e]

However, if we do this you might notice that this only returns '0.0000' because your values are so small. I would simply ignore this conversion entirely.

Next, you plot the y-axis as log with plt.yscale('log') however your y values are all below 0. This typically does not work and can be seen from the error:

Data has no positive values, and therefore cannot be log-scaled.

Perhaps for your real data this is not a problem.

Combing all of this leads to the following code:

import matplotlib.pyplot as plt


x = [0.0, 1e-07, 1.20226443461741e-07, 1.31825673855641e-07, 1.44543977074593e-07, 1.58489319246111e-07,
         1.73780082874938e-07, 1.90546071796325e-07, 2.08929613085404e-07, 2.29086765276777e-07,
         2.51188643150958e-07, 2.75422870333817e-07, 3.01995172040202e-07, 3.31131121482591e-07,
         3.63078054770101e-07]


y = [-0.887961849042741, -0.887961849042741, -0.887961849042949, -0.887961849043086, -0.887961849043252,
         -0.887961849043453, -0.887961849043695, -0.887961849043987, -0.88796184904434, -0.887961849044765,
         -0.887961849045278, -0.887961849045896, -0.887961849046641, -0.887961849047538, -0.887961849048619]


spec_x = [0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18,
         0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 10.0]
spec_x = [format(x,'f') for x in x1_l2]

spec_y = [0.638219, 0.321497, 0.216958, 0.165437, 0.135094, 0.115313, 0.101539, 0.0914968, 0.0839203, 0.078051,
         0.073407, 0.0696679, 0.066613, 0.0640855, 0.0619714, 0.0601859, 0.0586651, 0.0573596, 0.0562311, 0.0552495,
         0.0543905, 0.0536349, 0.052967, 0.0523738, 0.0518448, 0.0513711, 0.0509454, 0.0505615, 0.0502142, 0.049899, 1.908654]


plt.plot(x, y, color='blue')
plt.plot(spec_x, spec_y, color='red', linestyle='dashed')

plt.xlabel('Frequencies (Hz)', fontsize=18)
plt.ylabel('Y Label', fontsize=16)

plt.xscale("log")
#plt.yscale("log")

plt.grid(which='major', color='#DDDDDD', linewidth=0.8)
plt.grid(which='minor', color='#EEEEEE', linestyle=':', linewidth=0.5)


# plt.xlim(min(spec_x), max(spec_x))
# plt.ylim(min(spec_y), max(spec_y))

Thanks! I did make sure that my original data doesn't have any negative values. Here are the values: justpaste.it/4rw8v and here is how its plotting ibb.co/t8YcnJ4
Its setting x and y axis as 10 ^2. I don't want that. I want them as values. Also, there are no negative values in my data, why its still plotting negative? Is it because its a log plot and its automatically converting?

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