Matlab comments

The lines that follow the initial % MATLAB comment lines in fixedbedreact.m set up default values for the seven optional parameters. Then we prepare for the MATLAB IVP solver ode.. . that solves our problem by using the function dydt to evaluate the right-hand side of our IVP (4.22). Having solved (4.22) we plot two curves of the solution to the two joint DEs. 

The user should now be in the MATLAB eommand window, whieh eontains some helpful eomments together with the MATLAB prompt . MATLAB eommands are typed after the prompt, and entered using Return (or Enter ). Terminating the eommand with will suppress the result of the eommand being printed in the eommand window. Comments are preeeded by the % symbol. 

For each session, we put the most important functions in a table for easy reference or review. The first one is on the basic commands and plotting. Try the commands as you read. You do not have to enter any text after the "%" sign. Any text behind a "%" is considered a comment and is ignored. We will save some paper and omit the results generated by MATLAB. If you need to see that for help, they are provided on our Web Support. There is also where we post any new MATLAB changes and upgrades. Features in our tutorial sessions are based on MATLAB Version 6.1, and Control System Toolbox 5.1. 

Save these statements in a file named, say, plotxy.m. Anything after the"%" sign is regarded as a comment, which you do not have to enter if you just want to repeat this exercise. After we have defined or updated the values of x and y in the Command Window, all we need is to enter "piotxy" at the prompt and MATLAB will do the rest. The key is to note that the M-file has no "read" or "input" for x and y. All statements in an M-file are simply executed in the Command Window. 

There is another easy way to "cheat." On UNIX/Linux workstations, open up a new text editor and enter your frequently used statements there. On Windows, you can use the really nice MATLAB Editor. You can copy-and-paste multiple commands back and forth between the text editor window and the MATLAB window easily. If you want to save the commands, you certainly can add comments and annotations. You can consider this text file as a "free-format notebook" without having to launch the Microsoft Word Notebook for MATLAB. 

A few comments and observations are appropriate. The quality of the initial guesses for the free concentrations of the components is more critical than in the Matlab Newton-Raphson routine introduced previously. The main disadvantage of the Solver, however, is the fact that it can only be applied to one instance. It cannot be dragged around on the spreadsheet like most other functions of Excel. It means, for our present example, that for each solution the Solver needs to be set up individually, defining the Set Target... 

We note that fzerotryl is a MATLAB function m file that is stored in its folder with the extension. m as fzerotryl.m. Our program code is annotated with comments following the % symbol. Anything that follows after a % symbol on a line of code is not executed in MATLAB. More on MATLAB files, their storage, creation, etc. is given in Section 1.2.5. Specific built-in MATLAB functions and their use, such as fzero in the code below, should always be scrutinized by our students for their input/output syntax etc. using the built-in help MATLAB command help fzero for example. 

Our MATLAB programs generally carry many comments after a % sign so that the reader can better understand what we do when and why. This will help our users to adapt our printed programs for other purposes. 

The percentage sign makes all that follows on the same line into commentary to be skipped during execution of the file. See p. 232 for details on how to effectively (un)comment whole blocks of MATLAB code. 

Note that almost all calling sequences of MATLAB function m files start with the function s name, such as runsolveadiabxy above, followed by a list of parameters in parentheses (. .. ). Our particular call runsolveadiabxy(285,305,1,8.5) uses the interval limits 285 and 305 for a as its first two parameters, followed by the values of / and 7 for a specific chemical reaction. In our m files the list of possible parameters is always explained in the first comment lines of code. Often one or several of the parameters are optional. If they are not specified in the calling sequence, they are internally set to default values inside the program, such as n and anno are here. 

Here is the MATLAB program neurocycle. m, which upon the user s specification and using MATLAB s (un)commenting feature, which places the symbol % at the start of comment lines, either plots all eight profiles, or one profile and one phase plot, or only one phase plot for relatively high values of the time parameter t, when the system has reached its periodic limit cycle. 

The commenting or uncommenting of MATLAB code line blocks can best be achieved from the MATLAB text editor window for an m file. Simply highlight a block of code lines via a mouse drag in the MATLAB text editor window, then click on the Text entry of the editor s toolbar and click Comment or Uncomment as appropriate. This action makes % commenting marks appear at or disappear from the front of each code line of the highlighted block. 

Next we display 13 single, double, or multiple plots drawn by our MATLAB program neurocycle.m of (a) the acetylcholine concentration profile in compartment (II) above the phase plot of the acetylcholine concentration in compartment (I) versus that in compartment (II), or (b) the limit cycle plot, or (c) the plot of all 8 profiles. We include interpretative comments on the solution s behavior in each case. 

First and foremost is the ability to make comments (statements that are not executed), by starting a line with the % sign. Anything after this is simply ignored by Matlab but helps make large m files comprehensible. 

The following Matlab function program finds the root of the cubic equation for [H+] in terms of Ac b and DIG resulting from the combination of the equations in 4A1.1 (a) and (b) above (Zeebe and Wolf-Gladrow, 2000). Input values are temperature, salinity, depth, Ac b and DIG and the outputs are/co, pH, [GO2], [HGO3 ] and [GO ]. Units and equilibrium constants used are indicated in the comment statements, which are preceded by a % sign. 

In MATLAB you write computer programs that are called m-files and are saved on your computer. The files can be used at any time by simply typing their name in the command line, and one m-file can use another m-file. You will want to include comments in your m-file that explain what the file does. This is done by inserting a % everything after % on a line is considered a comment. These comments remind you of details when you come back to the program at a later time. 

Practical calculations of the electron density maps were performed with the program MATLAB R2013a by The MathWorks (USA). For this a program code was written which is listed below. Comments in the code are marked with the symbol % . 

Weaknesses Although the documentation provided has some helpfiil comments, it would be difficult for users that do not have some familiarity with Matlab to fiilly utilize this program—especially when it comes to tronbleshooting. 

Needless to say that within MATLAB we have all the algebraic, statistical functions predefined along with plotting capabilities. Before briefly commenting on the basics, it is interesting to point out the use of help within the command window. We use the help function followed by any built-in function and MATLAB returns a small tutorial on the use of that function, the arguments, and the options (i.e., try help ode45 ). 

We use to include a comment within the code. We solve the linear equation. MATLAB typically uses LU decomposition for this ... 

The first line defines the function xpowers, which has two outputs sq and cube and one input. The second line is a comment statement that is used to tell what xpowers is all about. The third and fourth lines calculate the values of input squared and cubed, respectively. While the main MATLAB window is active, press CTRL+N to activate the MATLAB m-file editor and paste the previous four lines. Save the file as xpowers.m. 

MATLAB generated comments were removed for easy code tracking... 

Commented lines immediately following the function declaration comprise the help file for the function. To obtain information on any function, simply type help function. Some MATLAB functions that are useful for process control include ... 

This section contains the MATLAB code for the examples considered in section Illustrative Examples. For educational purposes, the code was written as readable as possible with numerous comments. As a result of this approach, the efficiency of the code was unavoidably scarified. 

The symbol % indicates that this line contains comments. The % sign, and what comes after it in that line, will be ignored at the time of execution. Return to the MATLAB command window and type ... 

Files with Excel/VBA or MATLAB programs for all of the examples in the book, any concluding comments for those programs, and solutions to all of the end-of-chapter exercises are available on a DVD from the publisher with a qualifying course adoption. Additionally, solutions to all of the end-of-chapter exercises are provided. When possible, concluding comments are included along with the programs. 

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