intensity of dought events

Hi, I have a drought duration over time file. So, it is the drought duration event where it contains consecutive months of negative value, so, i need to calculate the mean intensity of each drought events, can I do it in matlab?

Answer 1

[Sulaymon Eshkabilov]

Use can use mean()

[Nurul Ain Basirah Zakaria]

can i just mean it like that? as the drought duration of each events is different?

[Sulaymon Eshkabilov]

MATLAB has a built in fcn mean() for 1D data and mean2() for 2D data. Yes, you can use these fcns w.r.t your data size.

[Nurul Ain Basirah Zakaria]

thank you sir! but out of my topic, can i detect the consecutive value from a range of data? for instance,

2 3 4 5 7 7 7 7 7 7 8 9 0 7 7 7 7 7 7 7 7 3 4 2 1

and then i want 7+7+7+7+7+7 divide by 6 as the first event, and then next consecutive 7, divide by 8? as the second event?

[Sulaymon Eshkabilov]

Here is a nice discussion on how to locate consequitive numbers:

https://www.mathworks.com/matlabcentral/answers/86420-find-a-series-of-consecutive-numbers-in-a-vector

You can find relevant comments and answers to this question of yours.

Answer 2

[Image Analyst]

You need to use regionprops(), which will get you both the length of each drought, as well as it's mean value. You can also get the max value if you want with 'MaxIntensity':

d = [1 -2 -2 -4 -5 -1 3 3 -3 -4.5 -8 5 6 7] % 2 regions of negative runs
% Find negative regions - binarize.
bw = d < 0
% Make measurements
props = regionprops(bw, d, 'Area', 'MeanIntensity');
% Get the lengths of all the runs
droughtDurations = [props.Area]
% Get the mean value for each of the 2 runs
droughtIntensities = [props.MeanIntensity]

You get:

bw =

1×14 logical array

0 1 1 1 1 1 0 0 1 1 1 0 0 0

droughtDurations =

5 3

droughtIntensities =

-2.8 -5.16666666666667

[Nurul Ain Basirah Zakaria]

so i can do this for my gridded data right? as i want to visualize it in spatial form

[Nurul Ain Basirah Zakaria]

my data is;

d=432x36x84

how can i want to plot it spatialy?

[Nurul Ain Basirah Zakaria]

and can i choose or put a condition where when it is a consecutive -ve value more than 1, it is not an event

[Image Analyst]

@Nurul Ain Basirah Zakaria, I have no idea. You did not attach your data in a .mat file with the paper clip icon, and you did not even describe what each dimension of your 3-D data means.

[Nurul Ain Basirah Zakaria]

i am sorry sir. this my data,

i calculated the spi index from precipitation data. Thus, now, i need to calculate the drought event, intensity and severity.

the d=432x36x84 is spixlatxlon

[Image Analyst]

Again, what does each of the 3 dimensions represent?

s=load('CHIRPS_SPI3_PT.mat')

s =

struct with fields:

CHIRPS_SPI3_PT: [420×15×7 double]

415 what??? 15 what??? 7 what???

[Nurul Ain Basirah Zakaria]

the 415 is the months/time from 1981-2016, and then, 15 is the no of grid of latitude and 7 is no of grid of longitude. can i apply the same step on my data? as at the end i want to produce a figure like this

[Image Analyst]

OK we're getting there. So, say for a given long and lat, what if there are 5 or 10 or 15 droughts of longer than a certain duration during those 415 months? How do you convert that to a color? Do you simply sum up all the drought months over the 415 months?

[Nurul Ain Basirah Zakaria]

i want it to be like this;

over the months of 415 months,

the consecutive -ve value, start with -ve and end with -ve value, is an event, so its okay if there are 5 or 10 or 15 drought months, as it is consecutive, it is a drought event.

the regionprops is okay but is it okay or can I apply it thru each grid over the 415 months?

is this okay sir?