Python scientific computing (1)

Use the python scientific computing library to achieve quick computing.

In standard Python, you can use list to save a set of values as an array. However, since the list element can be any object, the list stores the object pointer. In this way, to save a simple list [1, 2, 3], you need
There must be three pointers and three integer objects. For numeric operations, this structure is obviously a waste of memory and CPU computing time.

The array module of numpy can solve this problem. The details are not described here. Here we mainly record some basic usage methods of matplotlib

• First plot

 
# First plot with matplotlib
 
 
ImportMatplotlib. pyplot as PLT
 
 
PLT. Plot ([1, 3, 2, 4])
 
PLT. Show ()
 
 
 
 
In order to avoid pollution of global namespace, It is stronugly recommended to never import like:
 
 
From <module> Import *
 
 
 
 

     
     
 
      
      
 
       
Simple plot
 
      
 
     
     
 
 
 
 
Import matplotlibAsMpl
 
 
Import matplotlib. pyplotAsPLT
 
 
Import numpyAsNP
 
 
X = NP. arange (0.0, 6.0, 0.1)
 
PLT. Plot (x, [XI ** 2ForXIInX], label ='First', linewidth = 4, color = 'black ')
 
 
PLT. Plot (x, [XI ** 2 + 2ForXIInX], label ='Second', color = 'red ')
 
 
PLT. Plot (x, [XI ** 2 + 5ForXIInX], label ='Third ')
 
PLT. axis ([0, 7,-1, 50])
 
 
PLT. xlabel (R"$ \ Alpha $", Fontsize = 20)
 
 
PLT. ylabel (R'Y ')
 
 
PLT. Title ('Simple plot ')
 
PLT. Legend (loc ='Upper left ')
 
 
PLT. Grid (True)
 
 
PLT. savefig ('Simple upload', DPI = 200)
 
 
Print MPL. rcparams ['Figure. figsize'] # Return 8.0, 6.0
 
Print MPL. rcparams ['Savefig. DPI '] # default to 100 the size of the PIC will be 800*600
 
 
# Print MPL. rcparams ['Interactive ']
 
 
PLT. Show ()
 
 
 
 
 
 
 
 
 
 
 

       
       
 
        
        
 
         
Decorate plot with styles and types
 
        
 
       
       
 
 
 
 
 
Import matplotlibAsMpl
 
 
Import matplotlib. pyplotAsPLT
 
 
Import numpyAsNP
 
X = NP. arange (0.0, 6.0, 0.1)
 
 
PLT. Plot (x, [XI ** 2ForXIInX], label ='First', linewidth = 4, color = 'black') # using color string to specify color
 
 
PLT. Plot (x, [XI ** 2 + 2ForXIInX],'R', label = 'second') # using abbreviation to specify color
 
PLT. Plot (x, [XI ** 2 + 5ForXIInX], color = (1, 0, 1, 1), label ='Third') # using color tuple to specify color
 
 
PLT. Plot (x, [XI ** 2 + 9ForXIInX], color ='# Bcd2ee', label = 'fourth') # using hex string to specify color
 
 
PLT. xticks (NP. arange (0.0, 6.0, 2.5 ))
 
PLT. xlabel (R"$ \ Alpha $", Fontsize = 20)
 
 
PLT. ylabel (R'Y ')
 
 
PLT. Title ('Simple plot ')
 
 
PLT. Legend (loc ='Upper left ')
 
PLT. Grid (True)
 
 
PLT. savefig ('Simple upload', DPI = 200)
 
 
Print MPL. rcparams ['Figure. figsize'] # Return 8.0, 6.0
 
 
Print MPL. rcparams ['Savefig. DPI '] # default to 100 the size of the PIC will be 800*600
 
# Print MPL. rcparams ['Interactive ']
 
 
PLT. Show ()
 
 
 

        
        
 
         
         
 
          
Types of Graph
 
         
 
        
        
 
 

        
        
 
         
         
 
          
Bars
 
         
 
        
        
 
Import matplotlib. pyplotAsPLT
 
 
Import numpyAsNP
 
Dict = {'A': 40, 'B': 70, 'C': 30, 'D': 85}
 
 
ForI, keyInEnumerate (dict): PLT. Bar (I, dict [Key]);
 
 
PLT. xticks (NP. arange (LEN (dict) + 0.4, dict. Keys ());
 
 
PLT. yticks (dict. Values ());
 
PLT. Grid (True)
 
 
PLT. Show ()
 
 
 

         
         
 
          
          
 
           
Pies
 
          
 
         
         
 
Import matplotlib. pyplotAsPLT
 
 
PLT. Figure (figsize = (10, 10 ));
 
X = [4, 9, 21, 55, 30, 18]
 
 
Labels = ['Swiss ', 'austria', 'Spain', 'italy', 'France ',
 
 
'Benelux ']
 
 
Explode = [0.2, 0.1, 0, 0, 0.1, 0]
 
PLT. Pie (x, labels = labels, explode = explode, autopct ='% 1.1f % ');
 
 
PLT. Show ()
 
 
 
 
 
 

          
          
 
           
           
 
            
Scatter
 
           
 
          
          
 
Import matplotlib. pyplotAsPLT
 
 
Import numpyAsNP
 
X = NP. Random. randn (12, 20)
 
 
Y = NP. Random. randn (12, 20)
 
 
Mark = ['S ', 'O',' ^ ', 'V','> ',' <', 'D', 'P', 'h', '8 ', '+', '*']
 
 
ForIInRange (0, 12 ):
 
PLT. scatter (X [I], Y [I], marker = mark [I], color = (NP. random. rand (1, 3), S = 50, label = STR (I + 1 ))
 
 
PLT. Legend ()
 
 
PLT. Show ()