Python: How can I use ggplot with a simple 2 column array?

Question

I try to use ggplot for python I have the following data:

power_data = [[  4.13877565e+04,   2.34652000e-01],
[  4.13877565e+04,   2.36125000e-01],
[  4.13877565e+04,   2.34772000e-01],
...
[  4.13882896e+04,   2.29006000e-01],
[  4.13882896e+04,   2.29019000e-01],
[  4.13882896e+04,   2.28404000e-01]]

And I want to represent it in ggplot with this:

print ggplot(aes(x='TIME', y='Watts'), data=power_data) + \
    geom_point(color='lightblue') + \
    geom_line(alpha=0.25) + \
    stat_smooth(span=.05, color='black') + \
    ggtitle("Power comnsuption over 13 hours") + \
    xlab("Time") + \
    ylab("Watts")

but get the error:

  File "C:\PYTHON27\lib\site-packages\ggplot\ggplot.py", line 59, in __init__
    for ae, name in self.aesthetics.iteritems():
AttributeError: 'list' object has no attribute 'iteritems'
>>>

I don't know what the line aes(x='TIME', y='Watts') should be doing.

How can I format the power_data list so I can use it with ggplot, I want first column reprezentedon a time x axis and second column on a power y axis?

If I am trying with the meat example it doesn't show nothing it only shows

>>> print (ggplot(aes(x='date', y='beef'), data=meat) + \
...     geom_line())
<ggplot: (20096197)>
>>>

What should I do to further show the graphic?

Answer 1

There were 3 important steps that I missed:

1) First the data needs to be in a format like this:

[{'TIME': 41387.756495162001, 'Watts': 0.234652},
 {'TIME': 41387.756500821, 'Watts': 0.236125},
 {'TIME': 41387.756506480997, 'Watts': 0.23477200000000001},
 {'TIME': 41387.756512141001, 'Watts': 0.23453099999999999},
...
 {'TIME': 41387.756574386003, 'Watts': 0.23558699999999999},
 {'TIME': 41387.756580046, 'Watts': 0.23508899999999999},
 {'TIME': 41387.756585706004, 'Watts': 0.235041},
 {'TIME': 41387.756591365003, 'Watts': 0.23541200000000001},
 {'TIME': 41387.756597013002, 'Watts': 0.23461699999999999},
 {'TIME': 41387.756602672998, 'Watts': 0.23483899999999999}]

2) Then the data needs to be decorated with DataFrame with

powd = DataFrame(data2)

3) Without the plt.show(1) the plot will not show

Here is the code to solve the above:

from pandas import DataFrame
data2 = []
for i in range(0,len(power_data)):
    data2.append({'TIME': power_data[i][0], 'Watts': power_data[i][1]})

powd = DataFrame(data2)
print powd

# the above can be changed with this line:
# powd = DataFrame(power_data, columns=['TIME', 'Watts'])
# see sugestion in comments 

print ggplot(aes(x='TIME', y='Watts'), data=powd) + \
    geom_point(color='lightblue') + \
    geom_line(alpha=0.25) + \
    stat_smooth(span=.05, color='black') + \
    ggtitle("Power comnsuption over 13 hours") + \
    xlab("Time") + \
    ylab("Watts")

Or alternatively in one pass without the for as provided in the comment:

powd = DataFrame(power_data, columns=['TIME', 'Watts'])
print ggplot(aes(x='TIME', y='Watts'), data=powd) + \
        geom_point(color='lightblue') + \
        geom_line(alpha=0.25) + \
        stat_smooth(span=.05, color='black') + \
        ggtitle("Power comnsuption over 13 hours") + \
        xlab("Time") + \
        ylab("Watts")

Answer 2

We can also use another function from ggplot library qplot to plot the graph. Assuming the above dataset power_data as input. We can plot it as:

import qplot from ggplot qplot(power_data[:,0], power_data[:,1], type='l')