That is, call-by-reference (pointers) is not used (although Matlab does have a new handle class that can implement this kind of mutation). I'm a newbie, so my mistake is probably super obvious. Matlab uses call-by-value semantics, meaning that (conceptually) all arguments are copied into the formal parameters of the function. The figure is created, but the actual lines are not drawn. The program should be able to interpret the input 'cos(x)' and then plot it using eval, but it doesn't seem work. Plot_handles(window_id) = plot(x_axis, y_x) a 13 str ' (x)7x-a' fh str2func (str) fh (3) Undefined function or variable 'a'. fh (3) ans 8 If you include workspace variables in your character vector, str2func creates the function handle, but MATLAB throws an error when you invoke the function handle. In Python, name functions must follow the same rules as naming variables. X1 = input('Type starting value (x): ' ) Call the anonymous function using the handle. We will use this name to call the function later in the program. Window_input = input('In which window do you want to plot your function? ', 's') į_x = input('Type a function f(x) : ', 's') So far I have this: function = createPlot(plot_handles)
It should also return the vector plot_handles (which contains the plot handles for the specified function at the same index/position as the window-id) to mainMenu.m for later use. The job of createPlot.m is to ask the user for a window-id as well as a function and then plot the function in that window.
A typical use of function handles is to pass a function to another function. It starts by calling the function createPlot.m with plot_handles (empty at first). A function handle is a MATLAB ® data type that represents a function. The next example executes the size function on a 3-dimensional array, returning the array dimensions in output variables d1, d2, and d3.Alright, so I have a m-file called mainMenu.m, which is the main program and it looks something like this: If an error is encountered, a message is displayed that names the demo that failed.Įval(demos(n,:),'') This example uses a function showdemo that runs a MATLAB demo selected by the user. For more information, see Create Function Handle. Any command that can be executed from the MATLAB prompt may be executed from a Mfile u sing eval. The feval function follows the same scoping and precedence rules as calling a function handle directly. Eval is an acronym for evaluating, which is exactly what it does: it evaluates MATLAB expressions. This for loop generates a sequence of 12 matrices named M1 through M12: The eval function is one of MATLAB’s most powerful and flexible commands. You can construct expression by concatenating substrings and variables inside square brackets: expression string1,int2str ( var ),string2. eval (function (b1,b2,b3.)) Description eval (expression) executes expression, a string containing any valid MATLAB expression. = eval('function(var)') % recommended syntax Syntax eval (expression) eval (expression,catchexpr) a1,a2,a3. eval(' = function(var)') % not recommended.The first syntax below avoids strict checking by the MATLAB parser and can produce untrapped errors and other unexpected behavior. Using the eval output argument list is recommended over including the output arguments in the expression string. If this is not the case, use the try.catch control flow statement in your code.Įxecutes function with arguments b1,b2,b3., and returns the results in the specified output variables. This syntax is useful when expression is a string that must be constructed from substrings. It covers more advanced programming concepts such as recursion, vectorization, function handles, algorithm efficiency and others. If expression produces an error, the error string can be obtained with the lasterr function. expression = Įxecutes expression and, if an error is detected, executes the catch_expr string.You can construct expression by concatenating substrings and variables inside square brackets: = eval(function(b1,b2,b3.))Įxecutes expression, a string containing any valid MATLAB expression. Firstly, anything in the python interface will give you that error if you pass it a MATLAB anonymous function: > py.print ( (x) x) Error using py.print Handle to MATLAB function ' (x)x' is not supported. Evaluate MATLAB commands, create and edit files, view results, acquire data. 1 Answer Sorted by: 1 I suspect that what you want can't directly be done.
#Call matlab function handle eval code#
Eval (MATLAB Functions) MATLAB Function ReferenceĮxecute a string containing a MATLAB expression Accepted Answer: Stephen23 I have the following code which does not work and I don't understand why: Theme Copy foo'name' name'C23' handle (var) eval (var) handle (foo) I get the following error: Theme Copy Error using eval Undefined function or variable 'name'. We can also pass one or more arguments/variables while calling a function.
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