Change value based on the values of another column
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I have a table with 2 columns and 6000 rows each. Sample values in the 1st column is like:
-0.00554
-0.00503
-0.00406
-0.00406
-0.00316
-0.00274
-0.00274
0
0
0
0
0
0
0.00233
0.00452
0.00552
0.00715
0.00831
0
0
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
0
0
0
0.00552
0.00715
0.00831
0.00715
0.00831
0
0
0
0
0
-0.00406
-0.00316
The corresponding values in the 2nd column will be starting from 1,2,3, etc. until the positive value changes again to negative value in the 1st column. To be more specific, 1st column will be having values starting with -ve sign followed by 0s and +ve values. So, the -ve value will be changing to +ve and again back to -ve. Once the -ve value show up again, the count on the 2nd column should start from 1 again. Please help me wih this.
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Réponse acceptée
Star Strider
le 5 Août 2022
Another approach —
v = [-0.00554
-0.00503
-0.00406
-0.00406
-0.00316
-0.00274
-0.00274
0
0
0
0
0
0
0.00233
0.00452
0.00552
0.00715
0.00831
0
0
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
0
0
0
0.00552
0.00715
0.00831
0.00715
0.00831
0
0
0
0
0
-0.00406
-0.00316];
sv = sign(v);
sv(sv>=0) = 1; % Adjust 'sign' Vector
pn = [0 strfind(sv.', [1 -1]) numel(v)]; % +vn To -ve Transition Indices
for k = 1:numel(pn)-1
idx = [pn(k) pn(k+1)-1]+1; % Index Range
Col2(idx(1):idx(2)) = (idx(1) : idx(2)) - (idx(1)-1); % Create Column #2 (As Row Vector)
end
Result = [v, Col2(:)] % Full Matrix
ResultMtx = [Result(1:10,:) Result(11:20,:) Result(21:30,:) Result(31:40,:)] % Display (Remove Later)
ResultEnd = Result(41:end,:) % Display (Remove Later)
.
10 commentaires
Star Strider
le 8 Août 2022
The values for ‘Input1’ are different, and I do not understand how either it or ‘Output’ are incremented.
I just do not see any sort of pattern here that lends itself to being coded.
Plus de réponses (2)
dpb
le 5 Août 2022
Modifié(e) : dpb
le 5 Août 2022
If there's always at least one zero before the new -ive value excepting the initial element, then
ix=find(diff(sign([0;x]))==-1);
will locate the beginng line of each section.
Or, actually, on reflection,
ix=find(diff(sign([0;x]))<0);
will find a transition from either 0 to -ive or +ive to -ive
Andrei Bobrov
le 5 Août 2022
v = [-0.00554
-0.00503
-0.00406
-0.00406
-0.00316
-0.00274
-0.00274
0
0
0
0
0
0
0.00233
0.00452
0.00552
0.00715
0.00831
0
0
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
-9.00000000000000e-05
0
0
0
0.00552
0.00715
0.00831
0.00715
0.00831
0
0
0
0
0
-0.00406
-0.00316];
s = sign(v);
p = diff([0;s]) == -1 & s == -1;
i = accumarray(cumsum(p),1);
x = ones(size(p));
x(p) = x(p) - [ 0;i(1:end-1)];
out = cumsum(x);
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