If I wanted to create an array of specified class I would use an approach like this. So creating an array of int looks like this:
Aint = int16.empty(5,0);
Aint(1) = 3;
And it works fine. Now I want to create an array of tf class objects. My approach was similar:
L = tf.empty(5, 0);
s = tf('s');
L(1) = s;
This gives me an error:
Error using InputOutputModel/subsasgn (line 57)
Not enough input arguments.
Error in tf_array (line 6)
L(1) = s;
I also made sure to display class(s) and it correctly says it's tf. What do I do wrong here?
As usual, the MATLAB documentation has an example for how to do this sort of thing:
sys = tf(zeros(1,1,3));
s = tf('s');
for k = 1:3
sys(:,:,k) = k/(s^2+s+k);
end
So, the problem likely is that the indexing L(1) is wrong, it needs to be L(:,:,1).
Do note that tf.empty(5, 0) is instructing to create a 5x0 array (i.e. an empty array). There is no point to this. You might as well just skip this instruction. Because when you later do L(:,:,1), you'll be increasing the array size any way (it starts with 0 elements, you want to assign a new element, it needs to reallocate the array). You should always strive to create the arrays of the right size from the start.
Related
I want to iterate through all classes and packages in a special path.
After that, I want to get the MethodList.
In the command window I can use following and it’s working fine:
a = ?ClassName;
a.MethodList(X);
Now I separate this into a function:
function s = befehlsreferenz(path)
s = what(path); % list MATLAB files in folder
for idx = 1:numel(s.classes)
c = s.classes(idx);
b = ?c;
b.MethodList(0);
end
end
I get an error:
Too many outputs requested. Most likely cause is missing [] around left hand side that has a comma separated list
expansion. Error in (line 7) b.MethodList(0);
While debugging I can see:
c: 1x1 cell = ‘Chapter’
b: empty 0x0 meta.class
Why is b empty? How can I get the methodlist?
1 Edit:
Here is an example class, also not working with it.
classdef TestClass
%TESTCLASS Summary of this class goes here
% Detailed explanation goes here
properties
end
methods
function [c] = hallo(a)
c = 1;
end
end
end
When struggling with operators in Matlab, it's typically the best choice to use the underlying function instead, which is meta.class.fromname(c)
Relevant documentation: http://de.mathworks.com/help/matlab/ref/metaclass.html
Further it seems s.classes(idx); is a cell, use cell indexing: s.classes{idx} ;
temp(i,1) = rand(1)*(pb(1,num).pos(i,1) - pw(1,num).pos(i,1));
This line gives the following error:
Error using ==> minus
Not enough input arguments.
The following are the definitions of pb and pw.
pw=struct('fitness',[],'pos',{});
pb=struct('fitness',[],'pos',{});
pos is a 2 x 1 array.
When tracking down errors like this, I break the problem up into smaller bits. Especially when the logic isn't readily apparent. Not only does it provide a path that can be used to step through your function using the debugger, but it also makes it more readable.
I've taken liberty with the intermediate variable names.
thisPb = pb(1,num);
thisPw = pw(1,num);
initialPos= pw.pos(i,1);
finalPos = pb.pos(i,1);
whos initialPos finalPos
temp(i,1) = rand(1) * (finalPos - initialPos);
The line with whos will print out the values. Make sure that finalPos and initialPos are both numbers.
One way that you can get this error is when num is an empty matrix.
The expression
>> s(x).a
can return a variable number of outputs, depending on the size of x.
If x = [1,2,3] for example, it will return three values (as long as s has at least three elements).
If x = [] on the other hand, then s(x).a will return no outputs, so the expression
>> disp(s(x).a)
will give you a Not enough input arguments error, which is almost certainly what you're seeing. You should check that num is not empty.
Are you sure, that all values are really initialised? Try to check this before your codeline.
disp(pb(1,num).pos(i,1))
disp(pw(1,num).pos(i,1))
temp(i,1) = rand(1)*(pb(1,num).pos(i,1) - pw(1,num).pos(i,1));
I need to output .mat files for the below data. I need one file to have cell (1,1) to be Mean_RPM_list1, cell (2,1) to be Mean_RPM_list2 etc. And then I need another file to have cell(1,1) to be Mean_Torque_list1 to have cell(1,1).....and so on.
Can anybody shed any light on this for me?
Also if someone knows how to automate me calling the matrices A and B so I could have A = [Mean_rpm1:Mean_rpmMAX], that would also be very helpful.
TIA for any help.
A = [Mean_rpm1 Mean_rpm2 Mean_rpm3 Mean_rpm4 Mean_rpm5 Mean_rpm6 Mean_rpm7 Mean_rpm8 Mean_rpm9 Mean_rpm10 Mean_rpm11 Mean_rpm12];
B = [Mean_torque1 Mean_torque2 Mean_torque3 Mean_torque4 Mean_torque5 Mean_torque6 Mean_torque7 Mean_torque8 Mean_torque9 Mean_torque10 Mean_torque11 Mean_torque12];
plot(A,B,'*')
for i = 1:num_bins;
bin = first + ((i-1)/10);
eval(sprintf('Mean_RPM_list%0.f = A;',bin*10));
eval(sprintf('Mean_Torque_list%0.f = B;',bin*10));
end
First of all this is really bad idea to create a set of variables with names different by numbers. As you can see it's very difficult to deal with such variables, you always have to use eval (or other related) statements.
It's much easier to create a cell array Mean_rpm and access its elements as Mean_rpm{1}, etc.
If the vectors are numeric and have the same size you can also make a 2D/3D array. Then access as Mean_rpm(:,:,1) etc.
Next, to store a cell array to a mat-file you have to create this array in MATLAB. No options (at least for now) to do it by parts in a loop. (But you can do it for numeric vectors and matrices using matfile object.) So why do you need this intermediate Mean_RPM_list variable? Just do Mean_RPM_list{bin*10} = A in your loop.
For your first question, if you already have those variables you have to use eval in a loop. Something like
A = [];
for k=1:K
eval(sprintf('A{k} = [A, Mean_rpm%d];',k));
end
You can also get names for all similar variables and combine them.
varlist = who('Mean_rpm*');
A = cell(1,numel(varlist);
for k = 1:numel(varlist)
eval('A{k} = varlist{k};');
end
Here is one without loop using CELL2FUN:
A=cellfun(#(x)evalin('base',x),varlist,'UniformOutput',0);
You should avoid having all these individual variables around in the first place. Data types like arrays, cell arrays and structure arrays exist to help you with this. If you want each variable to be associated with a name, you can use a structure array. I've made an example below. Instead of assigning a value to Mean_rpm1 like you are doing now, assign it to meanStruct.Mean_rpm1 then save the entire structure.
% as you generate values for each variable, assign them to the
% appropriate field.
meanStruct.Mean_rpm1 = [10:10];
meanStruct.Mean_rpm2 = [12:15];
meanStruct.Mean_rpm3 = [13:20];
meanStruct.Mean_rpm4 = [14];
meanStruct.Mean_rpm5 = [15:18];
meanStruct.Mean_rpm6 = [16:20];
meanStruct.Mean_rpm7 = [17:22];
meanStruct.Mean_rpm8 = [18:22];
meanStruct.Mean_rpm9 = [19:22];
meanStruct.Mean_rpm10 = [20:22];
meanStruct.Mean_rpm11 = [21:22];
meanStruct.Mean_rpm12 = [22:23];
% save the structure array
save('meanValues.mat','meanStruct')
% load and access the structure array
clear all
load('meanValues.mat')
temp = meanStruct.Mean_rpm3
I was just wondering if there is a clean way to store a matrix after each iteration with a different name? I would like to be able to store each matrix (uMatrix) under a different name depending on which simulation I am on eg Sim1, Sim2, .... etc. SO that Sim1 = uMatrix after first run through, then Sim2 = uMatrix after 2nd run through. SO that each time I can store a different uMatrix for each different Simulation.
Any help would be much appreciated, and sorry if this turns out to be a silly question. Also any pointers on whether this code can be cleaned up would be great too
Code I am using below
d = 2;
kij = [1,1];
uMatrix = [];
RLABEL=[];
SimNum = 2;
for i =1:SimNum
Sim = ['Sim',num2str(i)] %Simulation number
for j=1:d
RLABEL = [RLABEL 'Row','',num2str(j) ' '];
Px = rand;
var = (5/12)*d*sum(kij);
invLam = sqrt(var);
u(j) = ((log(1-Px))*-invLam)+kij(1,j);
uMatrix(j,1) = j;
uMatrix(j,2) = u(j);
uMatrix(j,3) = kij(1,j);
uMatrix(j,4) = Px;
uMatrix(j,5) = invLam;
uMatrix(j,6) = var;
end
printmat(uMatrix,'Results',RLABEL,'SECTION u kij P(Tij<u) 1/Lambda Var')
end
There are really too many options. To go describe both putting data into, and getting data our of a few of these methods:
Encode in variable names
I really, really dislike this approach, but it seems to be what you are specifically asking for. To save uMatrix as a variable Sim5 (after the 5th run), add the following to your code at the end of the loop:
eval([Sim ' = uMatrix;']); %Where the variable "Sim" contains a string like 'Sim5'
To access the data
listOfStoredDataNames = who('Sim*')
someStoredDataItem = eval(listOfStoredDataNames {1}) %Ugghh
%or of you know the name already
someStoredDataItem = Sim1;
Now, please don't do this. Let me try and convince you that there are better ways.
Use a structure
To do the same thing, using a structure called (for example) simResults
simResults.(Sim) = uMatrix;
or even better
simResults.(genvarname(Sim)) = uMatrix;
To access the data
listOfStoredDataNames = fieldnames(simResults)
someStoredDataItem = simResults.(listOfStoredDataNames{1})
%or of you know the name already
someStoredDataItem = simResults.Sim1
This avoids the always problematic eval statement, and more importantly makes additional code much easier to write. For example you can easily pass all simResults into a function for further processing.
Use a Map
To use a map to do the same storage, first initialize the map
simResults = containers.Map('keyType','char','valueType','any');
Then at each iteration add the values to the map
simResults(Sim) = uMatrix;
To access the data
listOfStoredDataNames = simResults.keys
someStoredDataItem = simResults(listOfStoredDataNames{1})
%or of you know the name already
someStoredDataItem = simResults('Sim1')
Maps are a little more flexible in the strings which can be used for names, and are probably a better solution if you are comfortable.
Use a cell array
For simple, no nonsense storage of the results
simResults{i} = uMatrix;
To access the data
listOfStoredDataNames = {}; %Names are Not available using this method
someStoredDataItem = simResults{1}
Or, using a slight level of nonesense
simResults{i,1} = Sim; %Store the name in column 1
simResults{i,2} = uMatrix; %Store the result in column 2
To access the data
listOfStoredDataNames = simResults(:,1)
someStoredDataItem = simResults{1,2}
Just to add to the detailed answer given by #Pursuit, there is one further method I am fond of:
Use an array of structures
Each item in the array is a structure which stores the results and any additional information:
simResults(i).name = Sim; % store the name of the run
simResults(i).uMatrix = uMatrix; % store the results
simResults(i).time = toc; % store the time taken to do this run
etc. Each element in the array will need to have the same fields. You can use quick operations to extract all the elements from the array, for example to see the timings of each run at a glance you can do:
[simResults.time]
You can also use arrayfun to to a process on each element in the array:
anon_evaluation_func = #(x)( evaluate_uMatrix( x.uMatrix ) );
results = arrayfun( anon_evaluation_func, simResults );
or in a more simple syntax,
for i = 1:length(simResults)
simResults(i).result = evaluate_uMatrix( simResults(i).uMatrix );
end
I would try to use a map which stores a <name, matrix>.
the possible way to do it would be to use http://www.mathworks.com/help/matlab/map-containers.html
I have a function that returns one or more variables, but as it changes (depending on whether the function is successful or not), the following does NOT work:
[resultA, resultB, resultC, resultD, resultE, resultF] = func(somevars);
This will sometimes return an error, varargout{2} not defined, since only the first variable resultA is actually given a value when the function fails. Instead I put all the output in one variable:
output = func(somevars);
However, the variables are defined as properties of a struct, meaning I have to access them with output.A. This is not a problem in itself, but I need to count the number of properties to determine if I got the proper result.
I tried length(output), numel(output) and size(output) to no avail, so if anyone has a clever way of doing this I would be very grateful.
length(fieldnames(output))
There's probably a better way, but I can't think of it.
It looks like Matthews answer is the best for your problem:
nFields = numel(fieldnames(output));
There's one caveat which probably doesn't apply for your situation but may be interesting to know nonetheless: even if a structure field is empty, FIELDNAMES will still return the name of that field. For example:
>> s.a = 5;
>> s.b = [1 2 3];
>> s.c = [];
>> fieldnames(s)
ans =
'a'
'b'
'c'
If you are interested in knowing the number of fields that are not empty, you could use either STRUCTFUN:
nFields = sum(~structfun(#isempty,s));
or a combination of STRUCT2CELL and CELLFUN:
nFields = sum(~cellfun('isempty',struct2cell(s)));
Both of the above return an answer of 2, whereas:
nFields = numel(fieldnames(s));
returns 3.