I have a table, which is :
t:([]a:1 3 2 1 2 3 3 2 1;b:10 20 30 40 50 60 70 80 90;c:100 200 300 400 500 600 700 800 900)
And I want all c to be 0 where a is equal to 2, and all be to be 0 where a is equal to 1.
Currently I have these two codes:
t:update b:0 from t where a=1
t:update c:0 from t where a=2
My question is how to combine these two lines of codes into one. Because I am working on a table which is far bigger than this simple example and it will take me a lot of rows of codes to do all the updates, which is too long.
You can use vector conditional for this:
update b:?[a=1;0;b], c:?[a=2;0;c] from t
Related
I wanted to ask any keen users here how to "filter out" bad values regarding a tremendous amount of a data matrix in matlab.
e.g: I have a MATLAB data file containing values 2*5000 (double) which represent x and y coordinates. How is it possible to delete all values above or under a certain limit?
or easier:
(matrix from data file)
1 2 4 134 2
3 5 5 4 2
or
1 2 4 9 2
3 5 5 234 2
setting a certain limit and delete column:
1 2 4 2
3 5 5 2
Find the "bad" elements, e.g. A < 0 | A > 20
Find the "good" columns, e.g. ~max(A < 0 | A > 20)
Keep the "good" columns / Remove the "bad" columns, e.g. A(:, ~max(A < 0 | A > 20))
I'm trying to reshape an array but I'm having some issues.
I have an array see image below and I'm trying to get it to look like / follow the pattern in the row highlighted in yellow. (note: I'm not trying to calculate the array but reshape it so it follows a pattern)
aa=[1:5;10:10:50;100:100:500]
aa_new=reshape(aa',[1 numel(aa)])
aa_new produces:
1 2 3 4 5 10 20 30 40 50 100 200 300 400 500
I'm trying to get:
1 2 3 4 5 50 40 30 20 10 100 200 300 400 500
Reverse the column numbers of every second row i.e.
aa(2:2:end,:) = aa(2:2:end, end:-1:1);
Now you're good to go with reshaping:
aa = reshape(aa.', 1, []);
If I have two lists:
a:1 2 3 4;
b:10 20 30 40;
I want to sum the product of the two lists within a window of 2. So the result set should be:
10 50 130 250
For example, to get the result of 130 it would be (2*20)+(3*30) = 130
sums 2 mavg '(a*b)
seems to get me part way there, but the window of 2 isn't being applied. I've tried experimenting with sum, sums, sum each, wavg, mavg, etc. and I am completely stuck. Could anyone help? Thanks!
This line should work for you:
2 msum a*b
as demonstrated here:
q)a:1 2 3 4
q)b:10 20 30 40
q)2 msum a*b
10 50 130 250
For more information about the keyword msum, you could check out the Kx Reference page:
https://code.kx.com/wiki/Reference/msum
Hope that helps!
Alternatively you could use the adverb each prior:
q)+':[a*b]
However this will only work with a window size of 2 and if your data contains null values this needs to be padded with 0:
q)+':[0^a*b2]
On a positive note it is faster than using msum in this situation.
q)\ts:1000000 +':[0^a*b2]
940 1264
q)\ts:1000000 2 msum a*b2
1556 1104
I have a matrix of 130 x 48 called originalMatrix that are broken up into 100 x 48 rows as "weekdayTimeRows" and 30 x 48 rows as weekendTimeRows.
I am extracting 10 rows from "weekdayTimeRows" based on a logic array called "holidayLogicArray" that returns 1 for the 10 rows i want to extract and 0 for other 90 rows. These 10 rows are based on HolidayArrayDate.
I arrange them as an empty set, and then add them to a different matrix called weekendTimeRows.
holidayLogicArray=ismember(weekdayTimeRows(:,1),HolidayArrayDate);
holidayTimeRows=weekdayTimeRows(holidayLogicArray,:);
weekdayTimeRows(holidayLogicArray,:)=[];
weekendTimeRows=[weekendTimeRows; holidayTimeRows];
At this point, weekendTimeRows has its 30 rows and then the new 10 rows under it making it 40 x 48 rows. I need to sort the new 10 rows so that they fill in the same sequence of a the ORIGINAL matrix.
Example: Row 1 of 10 in holidayTimeRows is row 15 in orignalMatrix which is between rows 3 and 4 in weekendTimeRows now, so row 1 of 10 will be inserted between rows 3 and 4 instead of row 31.
NOTE: Time is random from values 1 to 130. They are NOT is ascending order. [so i cant use "sort" function]
ok it seems like a simple problem, but i am having problem
I have a timer for each data set which resets improperly and as a result my timing gets mixed.
Any ideas to correct it? without losing any data.
Example
timer col ideally should be
timer , mine reads
1 3
2 4
3 5
4 6
5 1
6 2
how do i change the colum 2 or make a new colum which reads like colum 1 without changing the order of ther rows which have data
this is just a example as my file lengths are 86000 long , also i have missing timers which i do not want to miss , this imples no data for that period of time.
thanks
EDIT: I do not want to change the other columns. The coulm 1 is the gps counter and so it does not sync with the comp timer due to some other issues. I just want to change the row one such that it goes from high to low without effecting other rows. also take care of missing pts ( if i did not care for missing pts simple n=1: max would work.
missing data in this case is indicated by missing timer. for example i have 4,5,8,9 with missing 6,7
Ok let me try to edit agian
its a 8600x 80 matrix of data:
timer is one row which should go from 0 to 8600
but timer starts at odd times , so i have start of data from middle , lets say 3400, so in the middle of day my timer goes to 0 and then back to 1.
but my other rows are fine. I just need 2 plot other sets based on timer as time.
i cannot use T= 1:length(file) as then it ignores missed time stamps ( timers )
for example my data reads like
timer , mine reads
1 3
2 4
3 5
4 8
5 9
8 1
9 2
so u can see time stamps 6,7 are missing.
if i used n=1:length(file)
i would have got
1 2 3 4 5 6 7
which is wrong
i want
1 2 3 4 5 8 9
without changing the order of other rows , so i cannot use sort for the whole file.
I assume the following problem
data says
3 100
4 101
5 102
NaN 0
1 104
2 105
You want
1 100
2 101
3 102
NaN 0
4 104
5 105
I'd solve the problem like this:
%# create test data
data = [3 100
4 101
5 102
NaN 0
1 104
2 105];
%# find good rows (if missing data are indicated by zeros, use
%# goodRows = data(:,1) > 0;
goodRows = isfinite(data(:,1));
%# count good rows
nGoodRows = sum(goodRows);
%# replace the first column with sequential numbers, but only in good rows
data(goodRows,1) = 1:nGoodRows;
data =
1 100
2 101
3 102
NaN 0
4 104
5 105
EDIT 1
Maybe I understand your question this time
data says
4 101
5 102
1 104
2 105
You want
1 4 101
2 5 102
4 1 104
5 2 105
This can be achieved the following way
%# test data
data = [4 101
5 102
1 104
2 105];
%# use sort to get the correct order of the numbers and add it to the left of data
out = [sort(data(:,1)),data]
out =
1 4 101
2 5 102
4 1 104
5 2 105
EDIT 2
Note that out is the result from the solution in EDIT 1
It seems you want to plot the data so that there is no entry for missing values. One way to do this is to make a plot with dots - there won't be a dot for missing data.
plot(out(:,1),out(:,3),'.')
If you want to plot a line that is interrupted, you have to insert NaNs into out
%# create outNaN, that has NaN-rows for missing entries
outNaN = NaN(max(out(:,1)),size(out,2));
outNaN(out(:,1),:) = out;
%# plot
plot(out(:,1),out(:,3))