Finding the maximum value in a single

I have a 1X128X3 single. I want to find the maximum values in each of the 3 channels, how can this be accomplished?

Answer 1

[John D'Errico]

The max function did not work? Why not? Surely you tried it?

S = rand([1,128,3],'single')

S = 1×128×3 single array
S(:,:,1) =

    0.9557    0.1427    0.3405    0.6756    0.9683    0.2260    0.2643    0.8766    0.1601    0.3533    0.1217    0.5791    0.1570    0.9396    0.3561    0.3374    0.2021    0.9924    0.1874    0.1094    0.4630    0.4364    0.3554    0.9370    0.0987    0.4981    0.1302    0.0768    0.9896    0.2384    0.1609    0.2545    0.5572    0.7844    0.8800    0.6078    0.1950    0.0075    0.5522    0.8453    0.3545    0.2669    0.8706    0.4797    0.9956    0.5484    0.8204    0.8800    0.3609    0.3253    0.5001    0.0510    0.7105    0.7387    0.3200    0.9856    0.8967    0.8876    0.0119    0.7305    0.6968    0.1452    0.9469    0.0811    0.7298    0.2679    0.5191    0.2916    0.8015    0.1417    0.0169    0.7617    0.3939    0.5777    0.0981    0.5780    0.8458    0.6728    0.6075    0.0170    0.4806    0.8411    0.5548    0.5855    0.0772    0.3482    0.1833    0.3835    0.7599    0.8728    0.3124    0.5976    0.1430    0.3458    0.6698    0.9066    0.1878    0.8884    0.8400    0.3497    0.1501    0.7870    0.3385    0.6183    0.9170    0.6736    0.6312    0.3466    0.2678    0.5486    0.7385    0.8791    0.3033    0.4010    0.8053    0.1195    0.7835    0.9073    0.9074    0.5491    0.4376    0.5875    0.8007    0.5016    0.3179    0.8934    0.3880    0.8169


S(:,:,2) =

    0.6750    0.0244    0.7297    0.7161    0.7345    0.3474    0.3519    0.9932    0.0022    0.5864    0.3253    0.5362    0.7495    0.2942    0.1847    0.4343    0.0366    0.6893    0.2565    0.9985    0.1643    0.4219    0.7648    0.7371    0.2732    0.6387    0.2065    0.8124    0.1072    0.3629    0.9866    0.8684    0.6886    0.7622    0.5557    0.5917    0.0315    0.2410    0.6593    0.9543    0.7830    0.0649    0.7360    0.6809    0.0108    0.3909    0.5070    0.6011    0.7611    0.3374    0.3473    0.1922    0.8107    0.5036    0.1575    0.3710    0.4097    0.7914    0.5949    0.7992    0.6088    0.0735    0.7162    0.6951    0.6174    0.0584    0.1226    0.9477    0.2845    0.3434    0.7580    0.7480    0.7757    0.7594    0.5944    0.2847    0.4666    0.2775    0.4339    0.0988    0.6698    0.0340    0.6814    0.6940    0.9222    0.1348    0.2211    0.8204    0.3004    0.6479    0.4911    0.9741    0.9958    0.2539    0.9974    0.3831    0.5335    0.0473    0.9102    0.7727    0.5120    0.8768    0.2086    0.8226    0.4095    0.4167    0.7353    0.1733    0.8169    0.5070    0.2328    0.2235    0.4618    0.0158    0.1165    0.4908    0.7861    0.4782    0.6259    0.3511    0.7469    0.7876    0.7971    0.5446    0.2603    0.1840    0.6295    0.9905


S(:,:,3) =

    0.4791    0.2940    0.6249    0.2390    0.0943    0.6676    0.3252    0.6926    0.2384    0.1067    0.8984    0.4460    0.0757    0.2423    0.4307    0.2851    0.2647    0.1595    0.0255    0.9026    0.6795    0.9780    0.7197    0.1265    0.1647    0.7993    0.6764    0.8225    0.9037    0.2253    0.2844    0.4565    0.2419    0.0760    0.8307    0.6283    0.8663    0.2074    0.8725    0.5262    0.3077    0.7511    0.6912    0.9238    0.1845    0.0062    0.9845    0.0728    0.5196    0.6840    0.5730    0.9710    0.1344    0.8643    0.8640    0.6774    0.0758    0.9000    0.1705    0.0219    0.8878    0.3826    0.9206    0.2563    0.6831    0.7040    0.0375    0.0802    0.7031    0.1078    0.7203    0.7382    0.4817    0.8284    0.8753    0.5169    0.1553    0.8930    0.8759    0.9566    0.7253    0.1547    0.8878    0.7939    0.9599    0.1355    0.5782    0.1458    0.3618    0.6818    0.3221    0.1438    0.7235    0.8641    0.4978    0.1295    0.8315    0.2729    0.4741    0.1573    0.9220    0.3514    0.3494    0.2594    0.7933    0.1565    0.6889    0.9444    0.4240    0.5562    0.2459    0.2756    0.4601    0.2840    0.9458    0.4839    0.6426    0.0580    0.7558    0.0852    0.7317    0.1730    0.2258    0.4086    0.4143    0.8189    0.0147    0.2181

Smax = max(S,[],2)

Smax = 1×1×3 single array
Smax(:,:,1) =

    0.9956


Smax(:,:,2) =

    0.9985


Smax(:,:,3) =

    0.9845

If you don't like that the result is now 1x1x3, use squeeze, or reshape to put it in the shape you prefer.

squeeze(Smax)

ans = 3×1

0.9956 0.9985 0.9845

Actually, a simple max(S) would also have worked, since max will apply to the first non-singleton dimension.

max(S)

ans = 1×1×3 single array
ans(:,:,1) =

    0.9956


ans(:,:,2) =

    0.9985


ans(:,:,3) =

    0.9845

So all you had to do was try the max function.

[Anwesh Saha]

Thank You for your response!

Answer 2

[Sulaymon Eshkabilov]

Here is how you can get max values from 1-by-n-by-3 array from each channel exaplined with a simple example:

PP(:,:,1) = round(10*randn(1,128), 2);
PP(:,:,2) = round(10*randn(1,128), 2);
PP(:,:,3) = round(10*randn(1,128), 2);
[Values, Index]=max(PP)

Values = 
Values(:,:,1) =

   25.7400


Values(:,:,2) =

   22.0600


Values(:,:,3) =

   26.9900

Index = 
Index(:,:,1) =

    56


Index(:,:,2) =

    30


Index(:,:,3) =

    93

% If the array is m-by-n-by-3:
P(:,:,1) = round(10*randn(20, 30), 2);
P(:,:,2) = round(10*randn(20, 30), 2);
P(:,:,3) = round(10*randn(20, 30), 2);
[Values, Index]=max(max(P))

Values = 
Values(:,:,1) =

   35.3400


Values(:,:,2) =

   30.0800


Values(:,:,3) =

   28.7700

Index = 
Index(:,:,1) =

    15


Index(:,:,2) =

    22


Index(:,:,3) =

     6