ndvi | python function that uses GDAL | Computer Vision library
kandi X-RAY | ndvi Summary
kandi X-RAY | ndvi Summary
A python function that uses GDAL and numpy to perform an NDVI calculation given a NIR band and a colour band. User can specify output as a 32-bit floating point image or a 16-bit unsigned integer image. Comes with a small clipping of a LANDSAT-8 surface reflectance image of Halifax, Nova Scotia, Canada for demo purposes. You should be able to demo it right out of the box provided the images are in the same directory as the script itself. Requires osgeo installation of GDAL and numpy (More info on NDVI:
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- Calculate an NDVI formula .
ndvi Key Features
ndvi Examples and Code Snippets
Community Discussions
Trending Discussions on ndvi
QUESTION
I am creating a new column using a vector value matching %in% operator
, but it returns NA
in the created column.
Any thoughts and solutions?
I used this chunk of code:
...ANSWER
Answered 2022-Apr-11 at 19:26The reason we are getting all NA
is because %in%
looks for a fixed match and not substring match. If we want to match based on substring, either use grepl
(from base R
) or str_detect
(from stringr
) to create logical vectors in case_when
.
QUESTION
I am performing a supervised classification with GEE on a region in Italy and I face the error: Output of image computation is too large (15 bands for 931221 pixels = 99.5 MiB > 80.0 MiB). If this is a reduction, try specifying a larger 'tileScale' parameter.
This is the part of the code that I think makes the problem because before these lines, I did not face errors:
...ANSWER
Answered 2022-Mar-28 at 12:03There are several factors that make your code heavy, including parameters for scale, amount of bands, tilescale, size of ICs etc.
I tested and was able to run your version with scale set to 120: https://code.earthengine.google.com/e18afb397b4954c6d841b7d7d5a2238a?accept_repo=users%2Fessepratico%2FPratico_et_al_RemoteSensing_2021
Also I experimented with using less bands, and was able to run at a scale of 50 without bands 1,6,7,8A.
You might want to see where you can reduce the amount of computing necessary to run the script. If you want to operate at a scale of 10 I would suggest to divide the region in smaller subsets.
QUESTION
I have a xarray data set and want to transform the values of my variable in a specific region within the dataset to Nan values. Using dataset.where I only get the specific region as the output but I want to keep the values at the locations around the mask in the array. So basically I want to keep my dataset but replace the values of my variable at certain coordinates with NaN.
[The dataset is called Lae21 and the lon/lat_mask are sliced coordinates from the dataset]
...ANSWER
Answered 2022-Mar-24 at 17:20I would use .loc
method for this:
QUESTION
I have a dataframe called data_subset
. In the aggregation_period
column, I want to replace every row containing month names (e.g, 3, 4, 5,6, 7) as an integer to month.abb format (e.g. Mar, Apr, May Jun, Jul) without affecting other rows containing AMJ and MAMJJ
. I have tried the below code chunks, but could not find a way to reach the required results.
Any thoughts and ideas, please?
...ANSWER
Answered 2022-Mar-22 at 06:04You can use an ifelse
statement to replace the values in the aggregation_period
column to integer if it's between 1 to 12, then use month.abb
to rename the values.
head()
and tail()
of the results are pasted here.
QUESTION
I have a long format data frame called ind_long_sub
. I want to select only characters such sum
or mean
from the characters in indices
column, so that I can create another column contain only characters such as mean
and sum
.
I have tried substr()
and strsplit()
functions, but could not achieved anything, because the characters in the column have different dimensions.
Any thoughts or ideas please?
...ANSWER
Answered 2022-Mar-19 at 07:59You could use str_extract
:
QUESTION
I fitted a glm model and had to transform some variables with log1p. I now want to create a ggpredict plot with a backtransformed scale. I transformed the variables before using the glm function.
here's a sample of a few variables of my original data and my code:
...ANSWER
Answered 2022-Mar-02 at 23:46When I can't get the built-in plot method to do what I want, I use ggpredict()
to get the predicted values and build the plot myself. I couldn't make your model work (you only gave us responses where case=1
) so I'm making up my own, slightly simpler example.
Load package and fit model:
QUESTION
When the user click for the first time on the map, he can see the related information. But if he click again, the informations are duplicated as you can see on the image below.
I expect that the old information is substitute with the newest. For handle this request I've developed the function below:
...ANSWER
Answered 2022-Feb-22 at 12:02The reason why you are getting more and more values/rows in your table for every click, is because you don't clear the table before adding data.
You need to call $("#"+elementID).html();
before $("#"+elementID).append(tableHead);
QUESTION
I'd like to use expand.grid
in vector to create all the combinations of the factors in myvec
, in a specific format and without duplicates. I try to:
ANSWER
Answered 2022-Feb-04 at 16:57If we need to create a single string for combinations from 2 to the length
of 'myvec', use combn
QUESTION
I would like to plot two different plots with Plotly on an HTML page, but only one will show.
I've tried to make Plotly.js plots based on this codepen.io I found but it will not display multiple plots properly. I have two CSV URLs. If I comment out one URL's code, the other will appear fine. However, if I include both code, only one will display and the other is blank. Is there a certain code I'm missing that will enable multiple plots to exist in an HTML site? I do not want to use subplot.
Partial code:
...ANSWER
Answered 2022-Jan-25 at 02:41I think there's a few things you can clean up in your code. It's better to reuse functions by adding more parameters rather than redefine the same function twice (and have to hardcode the data and div tag into each function definition)
I restructured your code so that the makeplot
function plots data from both url1
and url2
, and added an additional divName
parameter so that you can reuse the processData
and makePlotly
functions.
You can find the jsfiddle here
QUESTION
I used the .combine command to convert two image collections into a two-band image collection (in the last line) to use in a function in the next step. This command is executed but writes 0 elements in the console. Where does this problem come from?
code link: https://code.earthengine.google.com/ed0992093ff830d926c7dd14403477c6
Code:
...ANSWER
Answered 2022-Jan-21 at 21:59ee.Image.combine() uses the system:ID
property to join the 2 images. See the documentation here. Since your images do not match, the resulting collection has no images.
A solution that should fit your needs utilizes the ee.Join.inner() to take advantage of the Date
property that you have created to join the 2 image collections. A similar question was answered here.
Using inner join, I was able to accomplish what appeared to be your goal of finding the difference in NDVI between the S2 and MODIS collections. The full working script can be found here: https://code.earthengine.google.com/dc45df1b7cf83723d53e9f7917975e2d
Code:
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Install ndvi
You can use ndvi like any standard Python library. You will need to make sure that you have a development environment consisting of a Python distribution including header files, a compiler, pip, and git installed. Make sure that your pip, setuptools, and wheel are up to date. When using pip it is generally recommended to install packages in a virtual environment to avoid changes to the system.
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