When I am trying to create a table using the following code:
sz = [4 3];
varTypes = ["double","datetime","string"];
varNames = ["Temperature","Time","Station"];
temps = table('Size',sz,'VariableTypes',varTypes,'VariableNames',varNames)
I get:
Error using table (line 254) Specify variable types as a cell array of character
vectors, indicating the type of each variable to be created.
Please help me to find what I am missing here. I am using MATLAB R2018a.
The error message indicates that you need to use single-quote char vectors for that syntax. (There were some rough edges regarding table creation and double-quote strings...). You can use cellstr to work around this in R2018a, like so:
sz = [4 3];
varTypes = ["double","datetime","string"];
varNames = ["Temperature","Time","Station"];
temps = table('Size',sz,'VariableTypes',cellstr(varTypes),...
'VariableNames',cellstr(varNames))
The ability to use the 'Size' input was brand new for 18a, in case you're hitting a bug and/or want a solution which will run on older versions of MATLAB, you could use a custom function which populates an empty table according to whatever defaults you want. More variable types could be added to this demo:
>> temps = emptyTable( 4, varTypes, varNames )
temps =
4×3 table
Temperature Time Station
___________ ____ _______
NaN NaT ""
NaN NaT ""
NaN NaT ""
NaN NaT ""
This is the function:
function tbl = emptyTable( nRows, varTypes, varNames )
tbl = table();
varTypes = cellstr(varTypes); % hande string/char/cellstr input
for ii = 1:numel(varTypes)
varName = varNames{ii};
switch varTypes{ii}
case 'double'
tbl.(varName) = NaN(nRows,1);
case 'datetime'
tbl.(varName) = NaT(nRows,1);
case 'string'
tbl.(varName) = repmat("",nRows,1);
end
end
end
Related
I am running a LASSO estimation method alongside a for loop.
Here is the code:
%Lasso
data = rand(246,3); %random data for illistrative purposes
XL1 = lagmatrix(data,1); %Lags the data matrix by one period
ydata = data; %Specifies the dependent variable
ydata([1],:)=[]; %Removes the top row due to the lagged X
XL1([1],:)=[]; %Removes the top row of the lagged X with become a NaN from lagmatrix
for ii = 1:3 %For loop to complete LASSO for all industries
y = ydata(:,ii); %y is the industry we are trying to forecast
rng default % For reproducibility, as the LASSO uses some random numbers
[B,FitInfo] = lasso([XL1],y,'CV',10,'PredictorNames',{'x1','x2','x3'});
idxLambdaMinMSE = FitInfo.IndexMinMSE;
ii
minMSEModelPredictors = FitInfo.PredictorNames(B(:,idxLambdaMinMSE)~=0)
end
The output that the LASSO provides is
ii = 1
minMSEModelPredictors =
1×1 cell array
{'x2'}
ii = 2
minMSEModelPredictors =
1×5 cell array
{'x1'} {'x2'} {'x3'}
ii = 3
minMSEModelPredictors =
1×2 cell array
{'x2'} {'x3'}
For the purposes of automating this, I need the result to be reported in the following manner,
Results = {[2],[1 2 3],[2 3]};
I know this is a long shot, but it would be helpful as the above is easy to type out but If I increase the dimensions, this becomes a very difficult task.
Each output of minMSEModelPredictors is a cell array of the form
minMSEModelPredictors = {'x1', 'x2', 'x3'};
We can use strrep to get rid of the 'x' (or just don't have an 'x' in your predictor names to begin with), and str2double to convert the cell array to a numeric array.
Then storing the results is trivial...
Result = cell(1,3); % Initialise output
for ii = 1:3
% stuff...
minMSEModelPredictors = FitInfo.PredictorNames(B(:,idxLambdaMinMSE)~=0);
Result{ii} = str2double( strrep( minMSEModelPredictors, 'x', '' ) );
end
I am using the following code to get all the possible combinations of the rows of a matrix.
function rComb(matrix)
rows = size(matrix,1)
for n = 1:rows
rowsCell = num2cell(matrix,2);
r = nchoosek(1:size(matrix,1),n);
out = cell2mat(reshape(rowsCell(r.',:).',n,1,[]))
end
end
Now I want to take the transpose of the out variable, and I am using this code.
function rComb(matrix)
rows = size(matrix,1)
for n = 1:rows
rowsCell = num2cell(matrix,2);
r = nchoosek(1:size(matrix,1),n);
out = cell2mat(reshape(rowsCell(r.',:).',n,1,[]))
transp = out'
end
end
And I am facing this error...!!
"Error using '
Transpose on ND array is not defined. Use PERMUTE
instead."
Can you solve this issue?
One more thing can a function give us multiple outputs like all the possible combinations of output? Like in the above code if I place ';' after out variable statement this function won't display anything :/.
Is it possible to flatten an array of arbitrarily nested arrays of integers into a flat array of integers in Matlab? For example,
[[1,2,[3]],4] -> [1,2,3,4]
Any kind of guidance will be helpful. Thanks.
For example,
a.c = [5,4];
a.b.a=[9];
a.b.d=[1,2];
a= b: [1x1 struct]
c: [5 4]
In this case, my output will be
output= [9,1,2,5,4]
I think you will have to adapt the flatten function from the file exchange to use struct2cell so something like this:
function C = flatten_struct(A)
A = struct2cell(A);
C = [];
for i=1:numel(A)
if(isstruct(A{i}))
C = [C,flatten_struct(A{i})];
else
C = [C,A{i}];
end
end
end
This results in:
a.c = [5,4];
a.b.a=[9];
a.b.d=[1,2];
flatten_struct(a)
ans =
5 4 9 1 2
So the order is in the order you declared your struct instead of in your example order which I presume is alphabetical. But you have control over this so it shouldn't be a problem.
I have a preliminary hack which does work but rather clumsily. It descends recursively, saving structure names and unpacking the returned structure at each "level" .
% struct2sims converter
function simout = struct2sims(structin)
fnam = fieldnames(structin);
for jf = 1:numel(fnam)
subnam = [inputname(1),'_',fnam{jf}];
if isstruct(structin.(fnam{jf}) ) ,
% need to dive; build a new variable that's not a substruct
eval(sprintf('%s = structin.(fnam{jf});', fnam{jf}));
eval(sprintf('simtmp = struct2sims(%s);',fnam{jf}) );
% try removing the struct before getting any farther...
simout.(subnam) = simtmp;
else
% at bottom, ok
simout.(subnam) = structin.(fnam{jf});
end
end
% need to unpack structs here, after each level of recursion
% returns...
subfnam = fieldnames(simout);
for kf = 1:numel(subfnam)
if isstruct(simout.(subfnam{kf}) ),
subsubnam = fieldnames(simout.(subfnam{kf}));
for fk = 1:numel(subsubnam)
simout.([inputname(1),'_',subsubnam{fk}])...
= simout.(subfnam{kf}).(subsubnam{fk}) ;
end
simout = rmfield(simout,subfnam{kf});
end
end
% if desired write to file with:
% save('flattened','-struct','simout');
end
As part of an image processing pipeline using 'regionprops' in Matlab I generate the struct:
vWFfeatures =
1631x1 struct array with fields:
Area
Centroid
MajorAxisLength
MinorAxisLength
Eccentricity
EquivDiameter
Where 'Centroid' is a Vector containing [x, y] for example [12.4, 26.2]. I would like to convert this struct to a table and save as a CSV file. The objective is to separate the 'Centroid' vector into two columns in the table labelled Centroid_X and Centroid_Y for example. I am not sure how to achieve this.
So far I have investigated using the 'struct2table' function. This ouputs the 'Centroid' as one column. In addition when I try to assign the output to a variable I get an error:
table = struct2table(vWFfeatures)
Error using struct2table
Too many output arguments.
I cannot understand this, any help please?
Since the original struct2table isn't available to you, you might want to implement specifically the behavior you're trying to achieve yourself.
In this case, this means extracting the values you want to save, (split the array,) then save the data:
data_Centroid = vertcat(vWFfeatures.Centroid); %// contains the centroid data
Centroid_X = data_Centroid(:,1); %// The first column is X
Centroid_Y = data_Centroid(:,2); %// the second column is Y
csvwrite('centroid.csv',data_Centroid); %// writes values into csv
If you want column headers in your csv, it gets complicated because csvwrite can only handle numeric arrays:
celldata = num2cell(num2str(data_Centroid)); %// create cell array
celldata(:,3) = celldata(:,4); %// copy col 4 (y data) into col 3 (spaces)
for i=1:length(celldata)
celldata{i,2} = ','; %// col 2 has commas
celldata{i,4} = '\n'; %// col 4 has newlines
end
celldata = celldata'; %'// transpose to make the entries come columnwise
strdata = ['Centroid_X,Centroid_Y\n',celldata{:}]; %// contains all as string
fid = fopen('centroid.csv','w'); % writing the string into the csv
fprintf(fid,strdata);
fclose(fid);
This is how I solved it in the end: extracted each field from struct used horzcat to join into a new array then defined headers and used csvwrite_with_headers, to ouput to csv.
wpbFeatures = regionprops(vWFlabelled, 'Area','Centroid', 'MajorAxisLength', 'MinorAxisLength', 'Eccentricity', 'EquivDiameter');
wpbArea = vertcat(wpbFeatures.Area);
wpbCentroid = vertcat(wpbFeatures.Centroid);
wpbCentroidX = wpbCentroid(:,1);
wpbCentroidY = wpbCentroid(:,2);
wpbFeret = max(imFeretDiameter(vWFlabelled, linspace(0,180,201)), [], 2);
wpbMajorAxisLength = vertcat(wpbFeatures.MajorAxisLength);
wpbMinorAxisLength = vertcat(wpbFeatures.MinorAxisLength);
wpbEccentricity = vertcat(wpbFeatures.Eccentricity);
wpbEquivDiameter = vertcat(wpbFeatures.EquivDiameter);
wpbFeatures = horzcat(wpbArea, wpbCentroidX, wpbCentroidY, wpbFeret, wpbMajorAxisLength, wpbMinorAxisLength, wpbEccentricity, wpbEquivDiameter);
headers = {'Area','CentroidX','CentroidY', 'Feret', 'MajorAxisLength', 'MinorAxisLength', 'Eccentricity', 'EquivDiameter'};
csvwrite_with_headers(strcat(PlateName, '_ResultsFeatures.csv'),wpbFeatures,headers);
I'm trying to figure out the function command in Matlab and im having some difficulties.
I'm trying to write a Matlab function named dna_replicate. It will replicate a given strand and return its partner strand
For example if the user enters ATGCATGCAHGCAGTC, it should return TACGTACGT CGTCAG
A-->T
G-->C if the user enters other than these 4 letters, there should be blank in the partner strand. Thank you for your help
This implementation should be faster, involving only a simple table look-up. Note that the table t is constructed only once when the function is first called.
function out = dna_replicate(in)
persistent t
if isempty(t)
t = blanks(256);
t('ATGC') = 'TACG';
end
out = t(in);
end
How about:
function out = dna_replicate(in)
in = upper(in); % Ensures all same case
A = in=='A';
T = in=='T';
C = in=='C';
G = in=='G';
out = in;
out(A) = 'T';
out(T) = 'A';
out(C) = 'G';
out(G) = 'C';
out(~(A|T|C|G)) = ' ';
while #Jirka cigler answer works, it uses a for loop as well as dynamically growing vector 'out'. As matlab is optimized for vector operations, this answer should perform better.
You can create a simple vectorized solution using the function ISMEMBER:
function outString = dna_replicate(inString)
[~,index] = ismember(upper(inString),'ACGT'); %# Find the indices of inStrings
%# letters in string `ACGT`
outString = 'ACGT '; %# Initialize outString to `ACGT` and a blank
outString = outString(5-index); %# Use inverted and shifted index to expand
%# outString to the size of inString
end
And here's a test:
>> dna_replicate('ATGCATGCAHGCAGTC')
ans =
TACGTACGT CGTCAG
I think it can be implemented as follows:
function out=dna_replicate(in)
for i=1:numel(in)
switch in(i)
case 'A'
out(i)= 'T';
case 'G'
out(i)= 'C';
case 'T'
out(i)='A';
case 'C'
out(i)='G';
otherwise
out(i)=' ';
end
end
this function has argument of type char
in='ATGCATGCAHGCAGTC'
and you can run
out=dna_replicate(in)
to get the same result as you want :-)