We have very strange error that I don't know why:
This code run with my laptop and is correct but It doesn't work with another
laptop(has the same matlab version) with this error TOO MANY INPUT ARGUMENT
In Line 10!
clear
syms b c d;
E=29000; I=240/144;
mab=2*E*I*(b)/18;
mba=2*E*I*(2*b)/18;
mbc=2*E*I*(2*b+c)/12-24;
mcb=2*E*I*(b+2*c)/12+24;
mbd=2*E*I*(2*b+d-3*.6/144)/12;
mdb=2*E*I*(b+2*d-3*.6/144)/12;
[tetb tetc tetd]=solve(mcb==0,mba+mbc+mbd==0,mdb==0,b,c,d)
c=tetc;
b=tetb;
d=tetd;
eval(mab)
Use which solve to check which function is called. Since they differ in your case (see comments), you can use the method given for this question to exactly specify the path for a function to use. See addpath and rmpath there.
Related
For example I have a 1*30 structure a.field, when I type a(:).field in command window it just iteratively display a(1).field, a(2).field,... However, when I was trying to assign a(:).field to another variable b, what b get is just a(1).field.
BTW, if I attampt to pass a(:).field to a function, Matlab just throws an error "too many input arguments".
What is the mechanism behind? My guess is that matlab threat colon equivlant to the first element during assignment, is that true?
You need to add brackets, otherwise matlab don't understand that your trying to store an array:
b = [a(:).field]
Another option that provide similar result:
b = horzcat(a(:).field)
It is occasionally convenient to use a function as a "constant" variable of sorts in MATLAB. But when I was using this feature recently, I ran into an unexpected error. When I run the MWE below, I get the error Undefined function or variable 'a'. despite the function being clearly available in the same file. When I comment out the if statement, the error goes away. This seems to imply that MATLAB is pre-interpreting a as a variable even though the variable assignment line is never reached, ignoring the fact that there is a function by the same name. Is this a MATLAB bug or is it somehow the desired behavior?
Here is the MWE:
function matlabBugTest( )
if false
a = 'foo';
end
a
end
function b = a()
b = 'bar';
end
Follow-up:
I know it seems weird to intentionally use the same name for a variable and a function, so I'll give an example of where this can be useful. For instance, you may want to use a function to store some constant (like a file path), but also want to be able to use a different value in case the function cannot be found. Such a case might look like:
if ~exist('pathConstant.m', 'file')
pathConstant = 'C:\some\path';
end
load(fullfile(pathConstant, 'filename.ext'));
I know that language design decisions are often difficult and complicated, but one of the more unfortunate consequences of MATLAB's choice here to ignore the function by the same name is that it breaks compatibility between functions and scripts/command line. For instance, the following runs without issue in a script:
if false
a = 'foo';
end
a
where the function a (shown above) is saved in its own file.
It has to do with how Matlab performs name-binding at compilation time. Because matlabBugTest has a line that assigns a value to a, a is determined to be a variable, and the later line with a is a reference to that variable and not a call to the local function. More modern versions of Matlab, like my R2015a install, gives a more clear error message:
At compilation, "a" was determined to be a variable and this variable is uninitialized. "a" is also a function name and previous versions of MATLAB would have called the
function. However, MATLAB 7 forbids the use of the same name in the same context as both a function and a variable.
It's not so much a bug, as it is an ambiguity introduced by the naming scheme that was given a default resolution method, which can be annoying if you have never encountered the problem before and m-lint doesn't mark it. Similar behavior occurs when variables are poofed into the workspace without initialization beforehand.
So the solution is to either change the name of the function or the variable to different things, which I would argue is good practice anyways.
In considering your follow-up example, I have noticed some interesting behavior in moving things around in the function. Firstly, if the function is either external or nested, you get the behavior discussed very well by Suever's answer. However, if the function is local, you can get around the limitation (at least you can in my R2014b and R2015a installs) by invoking the function prior to converting it to a variable as long as you initialize it or explicitly convert it to a variable at some point. Going through the cases, the following bodies of matlabBugTest perform thusly:
Fails:
a
if false
a = 'foo';
end
a
Runs:
a
if true
a = 'foo';
end
a
Runs:
a = a;
if false % runs with true as well.
a = 'foo';
end
a
I'm not entirely sure why this behavior is the way it is, but apparently the parser handles things differently depending on the scope of the function and the order of what symbols appear and in what contexts.
So assuming this behavior hasn't and will not change you could try something like:
pathConstant = pathConstant;
if ~exist('pathConstant.m', 'file')
pathConstant = 'C:\some\path';
end
load(fullfile(pathConstant, 'filename.ext'));
Though, entirely personal opinion here, I would do something like
pathConstant = getPathConstant();
if ~exist('pathConstant.m', 'file')
pathConstant = 'C:\some\path';
end
load(fullfile(pathConstant, 'filename.ext'));
Concerning breaking "compatibility between functions and scripts/command line", I don't really see this as an issue since those are two entirely different contexts when it comes to Matlab. You cannot define a named function on the command line nor in a script file; therefore, there is no burden on the Matlab JIT to properly and unambiguously determine whether a symbol is a function call or a variable since each line executes sequentially and is not compiled (aside from certain blocks of code the JIT is designed to recognize and optimize like loops in scripts). Now as to why the above juggling of declarations works, I'm not entirely sure since it relies on the Matlab JIT which I know nothing about (nor have I taken a compiler class, so I couldn't even form an academic reason if I wanted).
The reason that you get this behavior is likely that Matlab never have implemented scope resolution for any of their statements. Consider the following code,
(a)
if true
a = 'foo';
end
disp(a)
This would actually display "foo". On the other hand would,
(b)
if false
a = 'foo';
end
disp(a)
give you the error Undefined function or variable "a". So let us consider the following example,
(c,1)
enterStatement = false;
if enterStatement
a = 'foo';
end
disp(a)
(c,2)
enterStatement = mod(0,2);
if enterStatement
a = 'foo';
end
disp(a)
TroyHaskin clearly states the following in his answer
It has to do with how Matlab performs name-binding at compilation time. Because matlabBugTest has a line that assigns a value to a, a is determined to be a variable, and the later line with a is a reference to that variable and not a call to the local function
Matlab does not support constant expressions and does only a limited amout of static code analysis. In fact, if the if statement takes argument false, or if enterStatement is false, Matlab provides a warning, This statement (and possibly following ones) cannot be reached. If enterStatement is set to false Matlab also generates another warning, Variable a is used, but might be unset. However if enterStatement = mod(0,2), so to say if enterStatement calls a function, you get no warning at all. This means that if the example in the question was allowed then (c,2) would compile based on how the function were evaluated and that is a contradiction. This would mean that the code would have to compile based on its runtime results.
Note: Sure it could be good if Matlab could generate an error in case the enterStatement was an expression instead of a constant false, but whether or not this is possible it would depend on implementation I guess.
Just having a little difficulty with the syntax of matlab functions;
function f = fact(x)
if x == 1
return
else
f = 1 - x*(fact(x-1))
end
end
When calling this function in the command window with the argument 10 I receive the error
Undefined function 'fact' for input arguments of type 'double'.
Error in recursion (line 6)
f = 1 - x*(fact(x-1))
I've had a look around and solutions for the first revolve around the pathing of the m-file which doesn't seem to be a problem as other files in the same directory run fine,
The second I'm not sure why the error in line 6 occurs, my guess is it has something to do with the variable and function names.
As a side question, are both these end statements necessary?
Thanks!
The most obvious error is your function filename. You have a function called fact defined in your code but you named your file recursion. Make sure that both your function name and the filename are both called fact.
If you were to name your file as recursion, then make the function name defined in your code as fact, this is what would happen if you tried calling your code:
>> f = recursion(10);
Undefined function 'fact' for input arguments of type 'double'.
Error in recursion (line 6)
f = 1 - x*(fact(x-1));
... look familiar?
As such make sure your filename and your function name are named the same. In fact, in the MATLAB editor, it should automatically give you an error saying that both of these are not the same.
There is also another error in your code. The base case is not defined properly. Always remember when you are writing recursive algorithms is that eventually the function is going to return... and that's when you hit the base case. We can see here that it is when x = 1. When x = 1, you're supposed to assign something to f which is the output. You are simply exiting the function, and so when x becomes 1, your code will spit out an error saying that f was not assigned when the function finishes. As such, you need to figure out what your base case is. I'm going to assume that your base case (when x = 1) is going to equal 0. You will obviously need to change this as I don't know what your code is actually computing. Basically, you need to do this:
function f = fact(x)
if x == 1
f = 0; %// Base case needs to change according to your specs
else
f = 1 - x*(fact(x-1))
end
end
When I do this, I get the following output when x = 10
>> f = fact(10);
f =
1334961
I don't get an error when I run this code now. Also, check to see if you have any variables named fact in your workspace. When this happens, you are in fact shadowing over your function with a variable, so it is actually trying to access the variable called fact instead. As such, try clearing your workspace by doing clear all;, then try this code again.
One warning
If you were to specify x to be 0 or negative, this function will never stop. As such, you need to provide some check and perform the proper action when this happens. Also, you need to make sure that you specify what type of inputs are accepted for x. Judging from the context, x are positive integers only. As what #Glen_b has noted, should you provide any number that isn't a positive integer, this function will never stop as x will never equal 1 down the recursion pipeline.
To answer your optional question
The first end statement is required to end the if statement. The second end statement isn't required, but it's good practice anyway. However, if you have multiple functions defined inside your function file, then yes it is most definitely required to properly signify that the end of that function is defined there. However, you don't need it if you're only writing one function per file, but I would recommend keeping it there as it's good practice.
[~,col] = find(ocpRefPt(2,:)>x1 & ocpRefPt(2,:)<x2 & ocpRefPt(1,:)>y1 & ocpRefPt(1,:)<y2);
About is the line where the compilation fails. The above line is in a loop.
x1,x2,x3,x4 are scalars(natural numbers)
ocpRefPt is a 2x16 matrix
Error: FIND requires variable sizing
What does this mean. How to overcome this error?
So it seems that you are trying to compile with emlmex to make embedded code. The error is saying that the size of the output of find is not known, and apparently the compiler requires fixed size outputs. See this newsgroup post for one explanation.
This method of compilation seems to be obsolete -- use the MATLAB coder (codegen command) instead:
emlmex Generate a C-MEX file from MATLAB code.
emlmex [-options] fun1 [fun2 ...]
This function is obsolete. For general purpose acceleration
and code generation use CODEGEN.
depfun's documentation gives the following:
[list,builtins,classes] = depfun(fun) returns the MATLAB classes that
fun requires.
Excellent, this is exactly what I want. However, when I call that on my function it tells me there are too many output arguments. So, I tried
list = depfun(Dynamo)
and to my surprise the same error occurred. How can this be? depfun(Dynamo) must return at least one argument, no?
What I'm trying to do is to create a dependency graph in the way as suggested by Andrew Janke in Automatically generating a diagram of function calls in MATLAB
The following works and gives me a nice report, but I don't want the graph to contain all the hidden functions which is why I'm opting for depfun.
profile on
Dynamo;
profile off
profview
Any insight is much appreciated
You need to pass the function argument as a string
>> [list,builtins,classes] = depfun( 'Dynamo' )