# 0.5 Writing c functions in matlab (mex-files)  (Page 3/3)

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```//---Inside mexFunction--- //DeclarationsmxArray *zData; int Num;//Copy input pointer z zData = prhs[2]; //Get the IntegerNum = (int)(mxGetScalar(zData)); //print it out on the screenprintf("Your favorite integer is: %d",Num);```

Three data types have been shown here. There are several others and the MATLAB help as well as the MATLAB example code shows how to use them. Now to export the data....

## Returning data to matlab

Assigning return values and data to the left hand side parameters is very similar to getting the data from the last section. The difference here is that memory must be allocated for thedata strucure being used on the output. Here is an example of how to return a 2-D matrix. This code will take the input x and return a copy of the matrix to z0 with every point in x multiplied by 2.Note that I am not copying the name of the output mxArray pointer into another variable.

```//---Inside mexFunction--- //DeclarationsmxArray *xData; double *xValues, *outArray;int i,j; int rowLen, colLen;//Copy input pointer x xData = prhs[0]; //Get matrix xxValues = mxGetPr(xData); rowLen = mxGetN(xData);colLen = mxGetM(xData); //Allocate memory and assign output pointerplhs[0] = mxCreateDoubleMatrix(colLen, rowLen, mxREAL); //mxReal is our data-type//Get a pointer to the data space in our newly allocated memory outArray = mxGetPr(plhs[0]); //Copy matrix while multiplying each point by 2for(i=0;i<rowLen;i++) {for(j=0;j<colLen;j++) {outArray[(i*colLen)+j] = 2*xValues[(i*colLen)+j]; }}```

## Calling built-in functions from a mex-file

While it may be nice to write functions in C, there are so many useful and fast pre-written functions in MATLAB that it would be a crime if we could not use them. Luckily,The Mathworks (creators of MATLAB) has provided this capability. Built-In functions have a parameter list similar to the mexFunction itself. This example uses the built-in function z = conv(x,y);

```//---Inside mexFunction--- //DeclarationsmxArray *result; mxArray *arguments[2]; //Fill in the input parameters with some trasharguments[0] = mxCreateDoubleMatrix(1, 20, mxREAL);arguments[1] = mxCreateDoubleMatrix(1, 10, mxREAL);//In the real world I imagine you would want to actually put //some useful data into the arrays above, but for this example//it doesnt seem neccesary. //Call the FunctionmexCallMATLAB(1,&result,2,arguments,"conv"); //Now result points to an mxArray and you can extract the data as you please!```

## Compiling

Compiling the MEX-Files is similar to compiling with gcc or any other command line compiler. In the MATLAB command prompt, change your current directory to thelocation of the MEX source file. Type: `mex filename.c` into the MATLAB command window. MATLAB may ask you to choose a compiler. Choose the compiler with MATLAB in its directory path.Your function will be called with the same name as your file. (ex: `mex jasonsFunction.c` produces a function that can be called from MATLAB as `[z0,z1] = jasonsFunction(x,y,z);` )

After compiling MATLAB produces the actual MEX binary that can be called as a normal MATLAB function. To call this function, you must be in the same directory with the binary. The binary goes by different namesdepending what system you compiled the source on (ex: Windows=.dll MacOSX=.mexmac Solaris=.mexsol Linux=.mexlx). Your MEX-function will have to be compiled on each type of system that you want to run it on because thebinaries are operating system specific.

## Other useful functions

Here is a nice list of useful functions in the mex library that make life a lot easier. Most of these work in similar fashion to those functions described above. The full list can be found inthe MATLAB help documentation with many examples. There are also some example files in the MATLAB extern directory (MATLAB/extern/examples/mx or mex).

• mxDuplicateArray
• mexErrMsgTxt
• mxMalloc
• mxRealloc
• mxCreateString
• mxDestroyArray
• mxFree
• mxGetCell
• mxGetData
• and many more...

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is this allso about nanoscale material
Almas
are nano particles real
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
no can't
Lohitha
where is the latest information on a no technology how can I find it
William
currently
William
where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
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Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
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