selection of certain data from matrix

Hi, my problem is that I have 3 matrix:

FlowMeasurements, psic_pos_cheb and psic_neg_cheb.

I need a matrix done this way with:

- all the columns of the psic_neg_cheb where FlowMeasurements is negative

- all the columns of the psic_pos_cheb where FlowMeasurements is positive.

For example, in this case it would be a matrix whith the 1-6 colums of psic_neg_cheb,

and after the 7-20 colums of psic_pos_cheb.

The matrixes are in attached

Answer 1

[Paul Rogers]

I finally did this way:

for i=1:length(FlowMeasurements)  
    if FlowMeasurements(i) < 0
        CompressorMapMatrix(:,i) = psic_neg_cheb (:,i);
    else
        CompressorMapMatrix(:,i) = psic_pos_cheb (:,i);
   
    end
end

Answer 2

[Walter Roberson]

mask_pos = FlowMeasurements > 0;
mask_neg = FlowMeasurements < 0;

pos_part = psic_neg_cheb(:,mask_pos);
neg_part = psic_neg_cheb(:,mask_neg);

I would often tend to use ~mask_pos instead of constructing an entirely new mask, but ~mask_pos would include <= 0 not just < 0 and that is perhaps not acceptable.

[Paul Rogers]

thanks mate, but not working.

neg_part

is ok, but

pos_part

gives me:

1,18756744635860	1,27884296305101	1,49473255111158	1,84984153587169	2,34531760870569	2,96764547395638	3,68901551096883	4,46925639509316	5,25915173457890	6,00480958865727	6,65263765281459	7,15440856338949	7,47188666387606	7,58053120154209
1,26236627545237	1,35364179214478	1,56953138020536	1,92464036496547	2,42011643779946	3,04244430305015	3,76381434006260	4,54405522418693	5,33395056367267	6,07960841775105	6,72743648190837	7,22920739248326	7,54668549296983	7,65533003063587
1,51401952583936	1,60529504253176	1,82118463059234	2,17629361535245	2,67176968818644	3,29409755343713	4,01546759044958	4,79570847457392	5,58560381405966	6,33126166813803	6,97908973229535	7,48086064287024	7,79833874335681	7,90698328102285
1,89436403494607	1,98563955163848	2,20152913969905	2,55663812445916	3,05211419729316	3,67444206254385	4,39581209955630	5,17605298368063	5,96594832316637	6,71160617724474	7,35943424140206	7,86120515197696	8,17868325246353	8,28732779012956
2,10054963540131	2,19182515209372	2,40771474015429	2,76282372491440	3,25829979774840	3,88062766299909	4,60199770001154	5,38223858413587	6,17213392362161	6,91779177769998	7,56561984185730	8,06739075243220	8,38486885291877	8,49351339058480

instead of this:

1,15485676094973	1,19451815030085	1,20412043363455	1,16897039548394	1,11900221787751	1,07932141846948	1,05306045991812	1,03637554207581	1,02571982389170	1,01883364616317	1,01439082605421	1,01162827719253	1,01011767563388	1,00964189492878
1,23149376578704	1,29087195834602	1,32225831933373	1,29380568524417	1,22661117478516	1,16146387859150	1,11377118354573	1,08191048649584	1,06104931872940	1,04739810325876	1,03853466279094	1,03300587840370	1,02997823192364	1,02902453044548
1,49091401583563	1,60746567066052	1,71123931432361	1,74520929512768	1,68139193321320	1,55973171029638	1,43671295235433	1,33877461070480	1,26827529760834	1,21971859774102	1,18730234541293	1,16677554308228	1,15544859561137	1,15187375450278
1,88335663640220	2,07518125588252	2,27599431090162	2,42140452584105	2,44078079902875	2,32434868034895	2,13399535699737	1,93993783821149	1,77860878301865	1,65777515160354	1,57311700475253	1,51802619627761	1,48718465039155	1,47740611693073
2,09611576761198	2,32652242543890	2,57651406489830	2,78091475505453	2,85678057787953	2,76993046876873	2,56931322938054	2,33680084232103	2,12863552830834	1,96553409962205	1,84812128633599	1,77049431074311	1,72666092137210	1,71272214474297

[Paul Rogers]

I see, it did't put rows and columns as it should, but it's anyway different values.

[Paul Rogers]

the proble is that it takes the first 6 columns of

psic_neg_cheb

which is right, and also the last 14th columns of

psic_neg_cheb

instead of

psic_pos_cheb