RE: Saving Large Matrices

*To*: mathgroup at smc.vnet.net*Subject*: [mg24807] RE: [mg24773] Saving Large Matrices*From*: "Tomas Garza" <tgarza at mail.internet.com.mx>*Date*: Sun, 13 Aug 2000 03:16:45 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

bbongiorno at attglobal.net wrote: > I need a effective way to store and retrieve a 300,000 x 44 matrix that > includes alpha numeric and numeric cells. > > The data is first downloaded from a database into a mathematica variable > in a note book. Included in some of the alpha numeric cells are commas, > tabs and spaces and therefore I cannot use Write function. If I use the > Write function to store the matrix, the integrity of the shape of the > matrix is impaired. > > The Export function works but it takes 24 hours to store the matrix on > a Pentium II 300 with major virtual memory usage. Try >> (Put). This will store your matrix in Mathematica format, and you can retrieve it with << (Get). Example: In[11]:= aMat = Table[Random[Integer, {0, 9}], {300000}, {44}]; // Timing Out[11]= {78.82 Second, Null} (It is quite large, indeed: it takes 78 seconds just to generate a random matrix that size). Now you store it in a file called "filaMat": In[12]:= aMat >> filaMat; // Timing Out[12]= {152.03 Second, Null} The storage process takes 152 seconds. Now you retrieve it: In[13]:= << filaMat; // Timing Out[13]= {159.45 Second, Null} The retrieval process takes 159 seconds. Tomas Garza Mexico City