I'm trying to finish a program and for some reason, the matrix I loaded into Matlab is messing with the ability to select the rows inside it. I'm trying to select all the rows in the matrix and see which values match the criteria for a Live setting. However I can select specific values/sections of the matrix in the command window without issue. Why is this happening? Any ideas?
It appears to only happen when in a for loop, I can do it just fine when it's on its own.
The syntax is: for x = start:stop. I think you are trying to do a for to the whole "A" matrix. You can split "A", according to its format (e.g. if is a table split in two variables).
bye
Richardd is right on; you're trying to iterate on a matrix, no good.
If I read you right, you're trying to run through your A matrix one column at a time, and see all the rows in that column? Assuming that is correct...
Your A matrix is 14x3, so you should go through your for loop 3 times, which is the size of your column dimension. Luckily, there is a function that MATLAB gives you to do just that. Try:
for iColumn = 1:size(A,2)
...
end
The size function returns the size of your array in a vector of [rows, columns, depth...] - it will go as many dimensions as your array. Calling size(A,2) returns only the size of your array in the column dimension. Now the for loop is iterating on columns.
Related
I need your help again :). I'm trying to plot multiple lines for a very large dataset. To start easier, I divided the dataset to get a TABLE in Matlab that contains 6 columns, with the first column representing the date that I want on my x-axis. Now I want to plot the other columns (and in the original file are a lot more than 6 columns) on the y axis, using a for loop. I tried the following, with no success:
hold on
for i=2:1:6
plot(Doldenstock(:,1), Doldenstock(:,i));
end
hold off
As I understand this, this code would do exactly what I want for columns 2,3,4,5,6. However, I always get the same error code:
Error using tabular/plot
Too many input arguments.
Error in Plotting_bogeo (line 6)
plot(Doldenstock(:,1), Doldenstock(:,i));
Now, I don't know if maybe for loops like this don't work for tabes but only for arrays?
Thanks for your help in advance!
Cheers,
Tamara
The function plot(x) expect x to be a scalar, a vector, or a matrix. But in your case the input is a table, because accessing a table with parentheses return a table, which is not supported.
If you read the doc "how to access data in a table" you will figure out that you need to use curly brace {} to extract the raw data (in your case a 1D matrix).
So use:
plot(T{:,1},T{:,2})
I want to read data from .txt file to plot a 3D graph in matlab. The data looks like this
T_hor T_ver V_hor V_ver
8,833 -15,43 -11,871 23,604
3,121 -22,78 -9,949 41,712
-8,012 -26,28 -4,317 33,790
-12,697 -20,99 6,948 22,314
-11,960 5,68 2,079 0,469
4,279 -22,17 -10,002 39,791
Each column I've imported as a separate column Vector say T_hor,T_ver,V_hor,V_ver. Now I want to read first 4096 rows of this individual column vector 'T_hor' and then the next 4096 rows of the column vector T_hor. This applies for every column. My Goal was to compute FFT for the 4096 set of values incrementally and store them as column vectors.I was previously using this command to read the values into different column vector.
x1 = T_ver(1:4096);
x2 = T_ver(4097:8193);
I want to make the code look more Logical and avoid unnecessary lines of code. So I tried applying for loop for this but I think I'm doing it in a wrong way.
for X
X = (1:LastValue:4096);
end
I think Vectorization can be more easy and consumes less execution time. Can anyone give me a direction or hints on how to implement this.
Hi and thank you for viewing my question.
I have a large spreadsheet (over 650,000 rows) that I am trying to spit up into separate parts of a structure. I am trying to split it up by the values in one of the columns of which there is 1132 unique text values. The rest of the columns are numerical. I have created a matrix of the numerical values with 4 columns called 'SectionID_Matrix' and a cell array for the text column I want to split the data up by called 'ELR'. I am also trying to name the parts in the structure by the text value I have split them up by. My code is as follows:
ELR_list = unique (ELR);
[m,~]=size(ELR_list);
n = 1;
b = [];
for j = 1:m
x = strcmp(ELR_list(n), char(ELR));
b(:,1) = SectionID_Matrix(x(:,1),1);
b(:,2) = SectionID_Matrix(x(:,1),2);
b(:,3) = SectionID_Matrix(x(:,1),3);
b(:,4) = SectionID_Matrix(x(:,1),4);
t = char(ELR_list(n));
s.(t) = b;
n = n+1;
end
clearvars -except *ELR_list* *ELR* *SectionID_Matrix* *s*
When I run this code though I get an error saying 'Subscripted assignment dimension mismatch'. Error in Sorting_Out_Locations (line 10). b(:,1) = SectionID_Matrix(x(:,1),1);
This is confusing me because when I remove the for loop and manually change the value of n, it works perfectly fine giving me a matrix in the structure with all the rows that contain the nth text value with the name of the text value.
I understand the error is caused by attempting to assign more elements to a section of a matrix or vector than that section can hold but I don't understand where that is happening.
Is there an error in my code that is causing the for loop to fail? because from my limited understanding the loop should just keep going around increase n by 1 each time until it has gone through all of the unique ELR values.
This is my very first time on Matlab (so any pointer on my code are very appreciated) and have spend all afternoon trying to get this working but no amount of internet help or the matlab website is helping.
Thank you for any help
In your code, the first time it runs through the loop, the size of the b matrix is set according to the number of true values in x. The next time it runs through the loop, that may be a different size, so you get the mismatch.
You can just clear b at the end of each loop iteration with b = []
The error Subscripted assignment dimension mismatch appears when you try to insert a matrix of a certain size into a matrix of a different size. For your code, it means that in the line
b(:,1) = SectionID_Matrix(x(:,1),1);
there is an attempted insertion of mismatching sizes: the size of SectionID_Matrix(x(:,1),1) and the size of b(:,1) are not the same. This is most likely because you only take certain values of each column of SectionID_Matrix using the logical indexing of x. To fix this you need the same logical indexing in b:
b(x(:,1),1) = SectionID_Matrix(x(:,1),1);
I have a list of text files that I would like to load, and then extract rows where they all overlap. The first column contains years and each data set spans a different chunk of years but they all overlap in the middle. In the end I would like to have a three dimensional matrix with the overlapping years in one matrix. My code keeps getting stuck at the line that I have commented out. I know its incorrect but could anyone tell me why it is incorrect?
clear all
name_list = {'Beijing';'GT';'soi';'naoi';'Sydney_Airport';'Los Angeles';'Paris';'Presque Isle'};
[m,n] = size(name_list);
files = dir('*.txt');
[m,n] = size(files);
for i=1:m
eval(['load ' files(i).name ' -ascii']);
vals{i} = load(files(i).name);
matrix = vals{i};
station = (files(i).name(1:end-4));
startyear(i) = min(matrix(:,1));
endyear(i) = max(matrix(:,1));
allstart = max(startyear);
allend = min(endyear);
%matrixnew(i) = matrix(allstart:allend,2:13,i);
end
Two problems here:
Your commented line %matrixnew(i) = matrix(allstart:allend,2:13,i); assumes that matrix is a 3-d array, but elsewhere you treat it as 2-d (and I believe that load always returns a 2-d array). This could be why you are getting the "Index exceeds matrix dimensions" error. Example:
>> foo = rand(10,10);
>> foo(2:10,3:4,2)
Index exceeds matrix dimensions.
Maybe you want matrix(allstart:allend,2:13)? But that won't work, because allstart contains a year, which presumably will not be a valid index for the array (a more likely cause of your error). Using the index that contains the smallest value would be closer to being correct, but I think it still won't work.
matrixnew refers to a single element of an array. You can't assign an array to an element of an array. grantnz is right that making matrixnew a cell array would fix this error, and I guess that in the end you could turn your cell array into 3-d array.
I think you are on the right track, but are missing a few pieces to making this work. One thing to consider is that it looks like you are trying to do everything in a single pass. I don't see how that can work. You need to real all files before you can decide which range of years to keep. So do it in multiple passes: first load all data from all files into a cell array, then figure out the range of years, then pull the data from each file for that range of years.
When I run this program, I get the error message:
??? Index exceeds matrix dimensions.
Error in ==> if a(1,i)==0
could you tell me why??
a = randi(5,4,100)-ones(4,100);
[n m]=size(a);
for i=1:m
if a(1,i)==0
a(:,i)=[];
end
end
The reason is that you are removing columns from your matrix, so inside the for loop you are reducing its dimension. Then you try to access a column with an index which refers to the original matrix, before the columns were removed.
Try this instead:
a = randi(5,4,100)-1;
ind2remove = (a(1,:) == 0);
a(:,ind2remove) = [];
You get that error because during the execution of this for loop, you might remove some columns. Therefore the dimensions of the matrix will decrease and you will try to access elements that have been moved to a different place.
To do wht you want, you either have to write a while loop, keeping the indices in check manually. The other solution is to vectorize your solution as itamar Katz has shown. That solution is more MATLAB-esque than writig a while loop.
But I have noticed that allowing a random algorithm to emit vectors of random length can sometimes prove more difficult to handle than fixed-length vectors. So you might want to construct your vector in such a way that you don't even have to remove such entries, depending on your application this might be accomplished by generating the first row and other rows with different instructions.