Make contour labels smaller?

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Abigail Waring
Abigail Waring on 12 May 2021
Commented: Abigail Waring on 4 Jun 2021
I have this contour map and the white labels are huge and I'm not sure how to reduce them and make them smaller.
Any ideas?
Heres the code
% ERA5_contourf_1
% Choose netcdf file
nc_file = '../data/ERA/ERA5_1979_1984.nc'; % put the full path to the netcdf file between the inverted commas
% Choose what time to plot (the nearest available data will be plotted)
chosen_time_datestr = '2008-06-29-10.00'; % edit this to plot different time-slices
chosen_time_datenum = datenum(chosen_time_datestr, 'yyyy-mm-dd-HH.MM');
%% Look at netcdf file metadata
% ncdisp(nc_file);
%
% Source:
% G:\sheffield_fellowship\teaching\pac_dissertations\2020_2021\abigail_waring\data\ERA\test 1979-2009.nc
% Format:
% 64bit
% Global Attributes:
% Conventions = 'CF-1.6'
% history = '2021-02-10 19:19:08 GMT by grib_to_netcdf-2.16.0: /opt/ecmwf/eccodes/bin/grib_to_netcdf -S param -o /cache/data3/adaptor.mars.internal-1612984616.206418-32671-22-77884e71-90b2-4259-9917-b6355929a1cd.nc /cache/tmp/77884e71-90b2-4259-9917-b6355929a1cd-adaptor.mars.internal-1612984616.2070854-32671-10-tmp.grib'
% Dimensions:
% longitude = 240
% latitude = 323
% time = 1575
% Variables:
% longitude
% Size: 240x1
% Dimensions: longitude
% Datatype: single
% Attributes:
% units = 'degrees_east'
% long_name = 'longitude'
% latitude
% Size: 323x1
% Dimensions: latitude
% Datatype: single
% Attributes:
% units = 'degrees_north'
% long_name = 'latitude'
% time
% Size: 1575x1
% Dimensions: time
% Datatype: int32
% Attributes:
% units = 'hours since 1900-01-01 00:00:00.0'
% long_name = 'time'
% calendar = 'gregorian'
% t2m
% Size: 240x323x1575
% Dimensions: longitude,latitude,time
% Datatype: int16
% Attributes:
% scale_factor = 0.001321
% add_offset = 278.4375
% _FillValue = -32767
% missing_value = -32767
% units = 'K'
% long_name = '2 metre temperature'
%% Open netcdf file
disp(['Loading ' nc_file]);
% Get variables from netcdf file
% Extract required variables
longitude = double(ncread(nc_file,'longitude')); % 'degree_east'
latitude = double(ncread(nc_file,'latitude')); % 'degree_north'
time = ncread(nc_file,'time'); % 'hours since 1900-01-01'
t2m = ncread(nc_file,'t2m')-273.15; % 'Centigrade'
t2m = permute(t2m,[2,1,3]);
% Prepare example data to plot
[lon_grid, lat_grid] = meshgrid(longitude, latitude);
t2m_eg = t2m(:,:,1);
% Convert to MATLAB time format
matlab_datetime = datetime(1900,1,1) + hours(time);
matlab_datetime = datenum(matlab_datetime);
% Get the closest data to the time indicated
[min_time_diff, min_time_diff_idx] = min(abs(matlab_datetime - chosen_time_datenum));
%% Load coastline
S = shaperead('../data/gshhs/GSHHS_shp/l/GSHHS_l_L1.shp', 'UseGeoCoords', true);
%% Plot example time-slice from netcdf file
disp('Plotting and saving a figure...');
% Make a figure
figure('units','normalized','outerposition',[0 0 1 1],'visible','on');
set(gcf,'color','w');
% Set axis font size
font_size = 12;
set(0, 'DefaultAxesFontSize', font_size);
% Make a map axis to encompass the data
ax = worldmap([nanmin(lat_grid(:)) nanmax(lat_grid(:))], ...
[nanmin(lon_grid(:)) nanmax(lon_grid(:))]);
% Allow overplotting
hold on
% Plot a pseudocolour plot of the chosen time-slice of the data
contourm(lat_grid, lon_grid, t2m(:,:,min_time_diff_idx), 'LevelStep', 5, ...
'LabelSpacing', 5, 'ShowText', 'on', 'fill', 'on', 'LineColor', [0.4 0.4 0.4]);
% Plot the gsshs coastlines using geoshow
geoshow(S, 'DisplayType', 'polygon',...
'FaceColor', 'none', 'EdgeColor', [0.1 0.1 0.1]);
% Make a colourbar
cbar = colorbar('eastoutside','fontsize',font_size);
% Add a colourbar label
set(get(cbar,'Xlabel'),'String','Temperature (^oC)');
% Add a scale bar
scb = scalebar('color',[0.3 0.3 0.3],'FontSize',font_size,'location','southeast');
% Add a title
title(datestr(matlab_datetime(min_time_diff_idx), 'HH.MM-dd-mm-yyyy'));
  2 Comments
Abigail Waring
Abigail Waring on 4 Jun 2021
Thank you @Benjamin worked perfectly!

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Answers (1)

DGM
DGM on 12 May 2021
Edited: DGM on 12 May 2021
It can be done, but it's a little awkward:
% this is just some test data
lat = 27.988056+(1:50);
lon = 86.925278+(1:50);
[lat lon] = ndgrid(lat,lon);
h = egm96geoid(lat,lon);
[c,hc] = contourm(lat,lon,h,'LevelStep',20,'ShowText','on');
axis equal
hch = get(hc,'children'); % labels and lines
hch = hch(isgraphics(hch,'Text')); % select only labels
set(hch,'fontsize',8) % set font size of all labels
Forgive the ugly example plot, but you get the idea.

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