I am wondering whether is it possible to make a table in netlogo where the left most/first column represents the agent-x who number (i.e agent-x 1, agent-x 2 ...) and the top/first row represents agent-y 's who number (i.e agent-y 23,agent-y 37).
The distances between the agents will be added to the corresponding cells. The result will be something similar to Excel, where if column B, contains agent-x 1 and row B contains agent-y 23 the corresponding cell for column B and row B will contain the distance between the two agents (i.e 8 units).
Related
I have a table (L-arrival) of 279 rows and 252 columns. Only the first column has values while others are just NaN. The cells in the first column have multiple values (i.e. some have 1, some have 4 number of values). First of all, I am trying to select a single maximum value from each cell of the first column so that I can have a column of a single value for each cell only. Then I want to do this in a loop so that for every new value that I get, they are sorted and only the maximum values are chosen. Finally, I want to make a collection of these values obtained from multiple runs for each cell. Can anyone suggest to me how it can be approached in MatLab?I tried using the following code but didn't work well.
for b=1:279
m = numel(cell2mat(L_arrival(b,1)));
g(b)=mat2cell([cell2mat(g(b)); cell(L_arrival(b,1))]',[1 2]);
end
I am learning KDB+ and Q programming and read about the following statement -
"select performs vector operations on column lists". What does Vector operation mean here? Could somebody please explain with an example? Also, How its faster than standard SQL?
A vector operation is an operation that takes one or more vectors and produces another vector. For example + in q is a vector operation:
q)a:1 2 3
q)b:10 20 30
q)a + b
11 22 33
If a and b are columns in a table, you can perform vector operations on them in a select statement. Continuing with the previous example, let's put a and b vectors in a table as columns:
q)([]a;b)
a b
----
1 10
2 20
3 30
Now,
q)select c:a + b from ([]a;b)
c
--
11
22
33
The select statement performed the same a+b vector addition, but took input and returned output as table columns.
How its faster than standard SQL?
"Standard" SQL implementations typically store data row by row. In a table with many columns the first element of a column and its second element can be separated in memory by the data from other columns. Modern computers operate most efficiently when the data is stored contiguously. In kdb+, this is achieved by storing tables column by column.
A vector is a list of atoms of the same type. Some examples:
2 3 4 5 / int
"A fine, clear day" / char
`ibm`goog`aapl`ibm`msft / symbol
2017.01 2017.02 2017.03m / month
Kdb+ stores and handles vectors very efficiently. Q operators – not just +-*% but e.g. mcount, ratios, prds – are optimised for vectors.
These operators can be even more efficient when vectors have attributes, such as u (no repeated items) and s (items are in ascending order).
When table columns are vectors, those same efficiencies are available. These efficiencies are not available to standard SQL, which views tables as unordered sets of rows.
Being column-oriented, kdb+ can splay large tables, storing each column as a separate file, which reduces file I/O when selecting from large tables.
The sentence means when you refer to a specific column of a table with a column label, it is resolved into the whole column list, rather than each element of it, and any operations on it shall be understood as list operations.
q)show t: flip `a`b!(til 3;10*til 3)
a b
----
0 0
1 10
2 20
q)select x: count a, y: type b from t
x y
---
3 7
q)type t[`b]
7h
q)type first t[`b]
-7h
count a in the above q-sql is equivalent to count t[`a] which is count 0 1 2 = 3. The same goes to type b; the positive return value 7 means b is a list rather than an atom: http://code.kx.com/q/ref/datatypes/#primitive-datatypes
Why does this not work?
cell2table({1;2;3},'RowNames',{'test'})
I have defined the data to be a cell column vector of numbers, and have specified a single heading.
I get the error:
Error using cell2table (line 58)
The RowNames property must contain one name for each row in the table.
creating a table with 1 row and 3 columns and the row named 'test':
cell2table({1 2 3},'RowNames',{'test'})
creating a table with 3 rows and 1 column and the cloumn named 'test':
cell2table({1;2;3},'VariableNames',{'test'})
you can also combine those, but 'Rownames'length hast to equal the amount of rows and 'Variablenames' length has to equal the amount of columns
I created a matrix with two columns, using two vectors, f and PS, that I already had:
M = [f PS]; %81x2 matrix
And then I sorted the matrix with respect to "PS" (second column), in order to have the maximum values of "PS" at the last positions of the vector:
M1=sortrows(M,2); %81x2 matrix
And I got something like this:
f...PS
5...83
10...136
3...357
1...985
Since now I assured the last two values of "PS" are indeed the maximum values, the information I want to give to the user is 1 and 3 (f values corresponding to the 2 maximum values of PS, which are at the bottom).
How can I do this?
You can use the end index: M1(end,1) and M1(end-1,1) should contain 1 and 3, respectively.
Best,
I'm trying to analyze data sets that are obtained from CSV files. After the data is read into matlab, I am left with a variable of my data only. The number of columns and rows changes between each file. Is there a way to average each column and then create a variable for the one with the closest average to a certain value? and then also select the columns directly before and after this middle column and create variables for them, as well as create a variable for the column with the lowest average? Currently, I am selecting the columns manually and creating a variables for them that way.
For example:
I have this table of numbers. (I used the same number in each column for sake of easy averaging in this example.
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
Let's say I want the column whose average is closest to 3.2
That column would be column 3 whose average is 3. Then I would want the code to select the column before (column 2) and the column after (column 4). As well as the column with the lowest average (column 1)
First get the averages (I assume the data matrix is in variable X):
Xmns = mean(X);
Then to find the minimum, use "min":
[val,ind] = min(Xmns);
"val" holds the minimum value, "ind" the corresponding index in Xmns, which is the corresponding column.
To find the column mean closest to a particular value, again you can use min:
[val,ind] = min(abs(Xmns-key_val));
Now "ind" holds the column index with mean closest to "key_val". The next column is just "ind+1" and the previous "ind-1" - just be sure to check you are not beyond the ends of the matrix (i.e. ind may already be 1 or size(X,2)).
Also, given the column index "ind", to create a new variable with that column, you just use:
sc= X(:,ind);
and if you want to remove that column from X:
X(:,ind) = [];
and that is all.