1Solving Systems of Equations9-14-20052Opening Discussion■What did we talk about last class?■Do you have any questions about the reading?3Structures■You can use the dot notation to put fields into a variable to make a structure. Unlike normal imperative languages, the format of the structure isn't predefined.■Matlab deals with arrays of structures just like numeric arrays.■The struct function can build arrays of structures from existing cell arrays.■You can pull out all the values of certain field with 'dynamic addressing'.4Strings■Like most other languages, Matlab does give you the ability to use strings, though that isn't a real strength.■A Matlab string is simply a row array of characters.■A downside of this is that an array with multiple strings must have all the strings be the same length. The char function can help with that.■You can also convert from numbers to strings and back with str2num and num2str.■Matlab also has fprintf and sprintf functions that work much like the C functions.■Similarly, sscanf will pull numbers out of strings.■eval and evalc let you process a string like it were a Matlab function.5Files■Save and load commands let you access native files that store Matlab variables.■Doing help fileformats will also show you all the other formats the Matlab supports normally.■You can do low level I/O with C-like functions. fopen, fclose, fread, fwrite, fscanf, fprintf, etc.■In addition, Matlab will also let you play with directories and even has built in support for ftp if you want to pull things across a network in Matlab.■Let's populate an array with a bunch of values, write it out in a text file, then read it back in.6Matrix Algebra■Now we get into the things that Matlab was really developed for and where it really stands out.■2-D arrays are basically matrices and can be used for doing all types of math.■Before we get into this we should talk about systems of linear equations and how they can be solved.■Matlab actually has routines that will try to solve systems of equations that aren't “well behaved”. That is, it will approximate both over-determined and under-determined systems.7Sparse Matrices■Matlab also has hat ability to store sparse matrices.■We aren't really going to take advantage of this in this class, but if you have a large matrix has has mostly zeros in it, this can be significant.8Reminders■Assignment #3 is due on
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