使用matplotlib和pandas从csv文件绘制直方图

Question

my csv file is very complex.. it contains numeric as well as string attributes. this is how my csv file looks like I want to plot a histogram of processes versus the cpuid

Answer 1

You can use read_csv , indexing with str and plot by hist :

import pandas as pd
import matplotlib.pyplot as plt
import io

temp=u"""kmem_kmalloc;{cpu_id=1}
kmem_kmalloc;{cpu_id=1}
kmem_kmalloc;{cpu_id=1}
kmem_kmalloc;{cpu_id=1}
kmem_kfree;{cpu_id=1}
kmem_kfree;{cpu_id=1}
power_cpu_idle;{cpu_id=0}
power_cpu_idle;{cpu_id=0}
power_cpu_idle;{cpu_id=3}"""

s = pd.read_csv(io.StringIO(temp), #after testing replace io.StringIO(temp) to filename
                sep=";", #set separator, if sep=',' can be omited (default sep = ,)
                header=None, #no header in csv
                names=[None,'cpuid'], #set names of columns, (first is None because index)
                index_col=0, #first column set to index
                squeeze=True) #try convert DataFrame to Series
print s
kmem_kmalloc      {cpu_id=1}
kmem_kmalloc      {cpu_id=1}
kmem_kmalloc      {cpu_id=1}
kmem_kmalloc      {cpu_id=1}
kmem_kfree        {cpu_id=1}
kmem_kfree        {cpu_id=1}
power_cpu_idle    {cpu_id=0}
power_cpu_idle    {cpu_id=0}
power_cpu_idle    {cpu_id=3}
Name: cpuid, dtype: object

#if max cpu <= 9, use Indexing with .str 
s = s.str[-2].astype(int)

#if cpu > 9 
#s= s.str.extract('(\d)', expand=False)
print s
kmem_kmalloc      1
kmem_kmalloc      1
kmem_kmalloc      1
kmem_kmalloc      1
kmem_kfree        1
kmem_kfree        1
power_cpu_idle    0
power_cpu_idle    0
power_cpu_idle    3
Name: cpuid, dtype: int32

plt.figure();
s.hist(alpha=0.5)
plt.show()